Targeting Subunit Research Articles

Tacrolimus Causes Hypertension by Increasing Vascular Contractility via RhoA (Ras Homolog Family Member A)/ROCK (Rho-Associated Protein Kinase) Pathway in Mice.

To provide tacrolimus is first-line treatment after liver and kidney transplantation. However, hypertension and nephrotoxicity are common tacrolimus side effects that limit its use. Although tacrolimus-related hypertension is well known, the underlying mechanisms are not. Here, we test whether tacrolimus-induced hypertension involves the RhoA (Ras homolog family member A)/ROCK (Rho-associated protein kinase) pathway in male C57Bl/6 mice. Intra-arterial blood pressure was measured under anesthesia. The reactivity of renal afferent arterioles and mesenteric arteries were assessed in vitro using microperfusion and wire myography, respectively. Tacrolimus induced a transient rise in systolic arterial pressure that was blocked by the RhoA/ROCK inhibitor Fasudil (12.0±0.9 versus 3.2±0.7; P<0.001). Moreover, tacrolimus reduced the glomerular filtration rate, which was also prevented by Fasudil (187±20 versus 281±8.5; P<0.001). Interestingly, tacrolimus enhanced the sensitivity of afferent arterioles and mesenteric arteries to Ang II (angiotensin II), likely due to increased intracellular Ca2+ mobilization and sensitization. Fasudil prevented increased Ang II-sensitivity and blocked Ca2+ mobilization and sensitization. Preincubation of mouse aortic vascular smooth muscle cells with tacrolimus activated the RhoA/ROCK/MYPT-1 (myosin phosphatase targeting subunit 1) pathway. Further, tacrolimus increased cytoplasmic reactive oxygen species generation in afferent arterioles (107±5.9 versus 163±6.4; P<0.001) and in cultured mouse aortic vascular smooth muscle cells (100±7.5 versus 160±23.2; P<0.01). Finally, the reactive oxygen species scavenger Tempol inhibited tacrolimus-induced Ang II hypersensitivity in afferent arterioles and mesenteric arteries. The RhoA/ROCK pathway may play an important role in tacrolimus-induced hypertension by enhancing Ang II-specific vasoconstriction, and reactive oxygen species may participate in this process by activating the RhoA/ROCK pathway.

MYPT1-PP1β phosphatase negatively regulates both chromatin landscape and co-activator recruitment for beige adipogenesis

Protein kinase A promotes beige adipogenesis downstream from β-adrenergic receptor signaling by phosphorylating proteins, including histone H3 lysine 9 (H3K9) demethylase JMJD1A. To ensure homeostasis, this process needs to be reversible however, this step is not well understood. We show that myosin phosphatase target subunit 1- protein phosphatase 1β (MYPT1-PP1β) phosphatase activity is inhibited via PKA-dependent phosphorylation, which increases phosphorylated JMJD1A and beige adipogenesis. Mechanistically, MYPT1-PP1β depletion results in JMJD1A-mediated H3K9 demethylation and activation of the Ucp1 enhancer/promoter regions. Interestingly, MYPT1-PP1β also dephosphorylates myosin light chain which regulates actomyosin tension-mediated activation of YAP/TAZ which directly stimulates Ucp1 gene expression. Pre-adipocyte specific Mypt1 deficiency increases cold tolerance with higher Ucp1 levels in subcutaneous white adipose tissues compared to control mice, confirming this regulatory mechanism in vivo. Thus, we have uncovered regulatory cross-talk involved in beige adipogenesis that coordinates epigenetic regulation with direct activation of the mechano-sensitive YAP/TAZ transcriptional co-activators.

The Effects of Cannabidiol on Aqueous Humor Outflow and Trabecular Meshwork Cell Signaling.

Intraocular pressure (IOP) is regulated primarily through aqueous humor production by ciliary body and drainage through uveoscleral and trabecular meshwork (TM) tissues. The goal of this study was to measure the effect of non-psychotropic cannabidiol (CBD) on aqueous humor outflow through TM and assess the effect of CBD on the TM cell signaling pathways that are important for regulating outflow. Perfused porcine eye anterior segment explants were used to investigate the effects of CBD on aqueous humor outflow. Cultured porcine TM cells were used to study the effects of CBD on TM cell contractility, myosin light chain (MLC) and myosin phosphatase targeting subunit 1 (MYPT1) phosphorylation, and RhoA activation. In the anterior segment perfusion experiments, aqueous humor outflow was increased significantly within 1 h after adding 1 µM CBD and the effect was sustained over the 5 h of measurement. Treatment of TM cells with 1 µM CBD significantly decreased TM cell-mediated collagen contraction, inhibited phosphorylation of MLC and MYPT1, and reduced RhoA activation. Our data demonstrate, for the first time, that as a potential therapeutic agent for lowering intraocular pressure, CBD can enhance aqueous humor outflow and modify TM cell signaling.

MYPT1 inhibits the metastasis of renal clear cell carcinoma via the MAPK8/N-cadherin pathway.

Myosin phosphatase target subunit 1 (MYPT1) is a subunit of myosin phosphatase that is capable of regulating smooth muscle contraction. MYPT1 has been reported to be involved in a wide variety of tumours, but its expression and biological functions in renal clear cell carcinoma (ccRCC) remain obscure. Herein, we analysed the relationship between patient clinicopathological characteristics and MYPT1 expression levels in ccRCC patients using a tissue microarray (TMA) and data retrieved from the TCGA-KIRC dataset. MYPT1 was overexpressed or depleted using siRNA in ccRCC cells to assess the effects on migration and invasion in vitro and in vivo. Additionally, RNA-sequencing and bioinformatics analysis were performed to investigate the precise mechanism. MYPT1 expression in ccRCC tissues was observed to be lower than that in nonmalignant tissues (P < 0.05). In addition, MYPT1 downregulation was closely linked to advanced pathological stage (P < 0.05), and poor OS (overall survival; P < 0.05). Functionally, increased expression of MYPT1 suppressed ccRCC migration and invasion in vitro, and inhibited tumour metastasis in vivo. In addition, MYPT1 overexpression exerted its suppressive effects via the MAPK8/N-cadherin pathway in ccRCC.

The Effect of Luteolin on the Modulation of Vascular Contractility via ROCK and CPI-17 Inactivation.

In this investigation, we made a study of the efficacy of luteolin (a flavonoid found in plants such as vegetables, herbs and fruits) on vascular contractibility and to elucidate the mechanism underlying the relaxation. Isometric contractions of denuded muscles were stored and combined with western blot analysis which was conducted to assess the phosphorylation of myosin phosphatase targeting subunit 1 (MYPT1) and phosphorylation-dependent inhibitory protein for myosin phosphatase (CPI-17) and to examine the effect of luteolin on the RhoA/ROCK/CPI-17 pathway. Luteolin significantly alleviated phorbol ester-, fluoride- and thromboxane mimetic-elicited contractions regardless of endothelial nitric oxide synthesis, implying its direct effect on smooth muscle. It also significantly alleviated the fluoride-elicited elevation in pCPI-17 and pMYPT1 levels and phorbol 12,13-dibutyrate-elicited increase in pERK1/2 level, suggesting depression of ROCK and PKC/MEK activity and ensuing phosphorylation of MYPT1, CPI-17 and ERK1/2. Taken together, these results suggest that luteolin-elicited relaxation includes myosin phosphatase reactivation and calcium desensitization, which seems to be arbitrated by CPI-17 dephosphorylation via ROCK/PKC inhibition.

Paeoniflorin alleviates liver injury in hypercholesterolemic rats through the ROCK/AMPK pathway.

Paeoniflorin (PF) is the main active component in Paeonia lactiflora Pall, and it has multiple effects. However, the precise mechanism of PF in hypercholesterolemia is unclear. In this study, rats were either fed a high-cholesterol diet (HCD) for 4 weeks to establish the hypercholesterolemic model or administered normal saline or PF (20 mg/kg/day). PF significantly reduced liver weight and the liver index. PF reduced hepatic lipid deposition and inflammation, improved serum lipid metabolism, and significantly inhibited serum and hepatic oxidative stress and the inflammatory response. PF treatment caused a marked decrease in the phosphorylated myosin phosphatase target subunit (p-MYPT)-1, nuclear sterol regulatory element-binding protein-1c (SREBP-1c), fatty acid synthase (FAS) levels, and an increase in the low-density lipoprotein receptor (LDLR) and phosphorylated-AMP-activated protein kinase (p-AMPK). Thus, PF could alleviate liver injury in hypercholesterolemic rats, and the specific mechanism may be related to the antioxidant, anti-inflammatory properties, and ROCK/AMPK/SREBP-1c signaling pathway.

Complex Transcriptional Profiles of the PPP1R12A Gene in Cells of the Circulatory System as Revealed by In Silico Analysis and Reverse Transcription PCR.

The myosin light chain phosphatase target subunit 1 (MYPT1), encoded by the PPP1R12A gene, is a key component of the myosin light chain phosphatase (MLCP) protein complex. MYPT1 isoforms have been described as products of the cassette-type alternative splicing of exons E13, E14, E22, and E24. Through in silico analysis of the publicly available EST and mRNA databases, we established that PPP1R12A contains 32 exons (6 more than the 26 previously reported), of which 29 are used in 11 protein-coding transcripts. An in silico analysis of publicly available RNAseq data combined with validation by reverse transcription (RT)-PCR allowed us to determine the relative abundance of each transcript in three cell types of the circulatory system where MYPT1 plays important roles: human umbilical vein endothelial cells (HUVEC), human saphenous vein smooth muscle cells (HSVSMC), and platelets. All three cell types express up to 10 transcripts at variable frequencies. HUVECs and HSVSMCs predominantly express the full-length variant (58.3% and 64.3%, respectively) followed by the variant skipping E13 (33.7% and 23.1%, respectively), whereas in platelets the predominant variants are those skipping E14 (51.4%) and E13 (19.9%), followed by the full-length variant (14.4%). Variants including E24 account for 5.4% of transcripts in platelets but are rare (<1%) in HUVECs and HSVSMCs. Complex transcriptional profiles were also found across organs using in silico analysis of RNAseq data from the GTEx project. Our findings provide a platform for future studies investigating the specific (patho)physiological roles of understudied MYPT1 isoforms.

MYPT1 reduction is a pathogenic factor of erectile dysfunction

Erectile dysfunction (ED) is closely associated with smooth muscle dysfunction, but its underlying mechanisms remains incompletely understood. We here reported that the reduced expression of myosin phosphatase target subunit 1 (MYPT1), the main regulatory unit of myosin light chain phosphatase, was critical for the development of vasculogenic ED. Male MYPT1 knockout mice had reduced fertility and the penises displayed impaired erections as evidenced by reduced intracavernous pressure (ICP). The penile smooth muscles of the knockout mice displayed enhanced response to G-Protein Couple Receptor agonism and depolarization contractility and resistant relaxation. We further identified a natural compound lotusine that increased the MYPT1 expression by inhibiting SIAH1/2 E3 ligases-mediated protein degradation. This compound sufficiently restored the ICP and improved histological characters of the penile artery of Mypt1 haploinsufficiency mice. In diabetic ED mice (db/db), the decreased expression of MYPT1 was measured, and ICP was improved by lotusine treatment. We conclude that the reduction of MYPT1 is the major pathogenic factor of vasculogenic ED. The restoration of MYPT1 by lotusine improved the function of injured penile smooth muscles, and could be a novel strategy for ED therapy.

Short-term mechanisms activated by NGF to induce pulmonary arterial hyperreactivity

We have previously shown a pathophysiological role for NGF in pulmonary hypertension, particularly in pulmonary arterial (PA) hyperreactivity. Our experiments have suggested different mechanisms activated by NGF depending on a short- or a long-term PA treatment. The aim of the present study was to determine the mechanisms activated by a short-term NGF treatment (1 h) to induce PA hyperreactivity. Contractions of rat PA were induced ex vivo by endothelin-1 (ET-1, 10-12-10-6 M) in the absence or presence of NGF (100 ng/mL, 1 h), with or without K252a (TrkA kinase inhibitor, 300 nM) or Y–27632 (ROCK inhibitor, 10 μM). NGF–induced phosphorylation of myosin phosphatase target subunit 1 (MYPT1) was evaluated in vitro by Western blotting in primary PA smooth muscle cells (PASMC) from both rat and human origin. Basal and ET–1–induced (10-7 M) calcium responses were evaluated in vitro in PASMC using calcium imaging (Fura2, Fluo-4), in the absence or presence of NGF (100 ng/mL, 1 h). Calcium sources involved in NGF-dependent increase in calcium levels and response to ET-1 were determined using Thapsigargin and Cyclopiazonic acid (SERCA inhibitors, 1 or 10 μM, respectively) or verapamil and Nicardipine (calcium L–Type channels blocker, 2 μM). Ex vivo, NGF (1 h) induced rat PA hyperreactivity to ET-1 in a TrkA- and ROCK-dependent manner. In vitro, in both rat and human PASMC, NGF (1 h) enhanced basal calcium levels through activation of calcium L-type channels. NGF also enhanced ET–1–induced increase in intracellular calcium levels, with endoplasmic reticulum (ER) being the main calcium source contributing to these effects. Finally, in both rat and human cells, NGF also induced phosphorylation of MYPT1 in a TrkA- and ROCK-dependent manner. In conclusion, our results show that NGF induces PA hyperreactivity to ET-1 through activation of its TrkA receptor, leading to both increased calcium intracellular levels and increased ER calcium loading. NGF also activates ROCK-dependent calcium sensitization mechanisms. Such mechanisms may therefore contribute to NGF-induced PA hyperreactivity in pulmonary hypertension.

MARK2 regulates directed cell migration through modulation of myosin II contractility and focal adhesion organization

Cancer cell migration during metastasis is mediated by a highly polarized cytoskeleton. MARK2 and its invertebrate homolog Par1B are kinases that regulate the microtubule cytoskeleton to mediate polarization of neurons in mammals and embryos in invertebrates. However, the role of MARK2 in cancer cell migration is unclear. Using osteosarcoma cells, we found that in addition to its known localizations on microtubules and the plasma membrane, MARK2 also associates with the actomyosin cytoskeleton and focal adhesions. Cells depleted of MARK proteins demonstrated that MARK2 promotes phosphorylation of both myosin II and the myosin phosphatase targeting subunit MYPT1 to synergistically drive myosin II contractility and stress fiber formation in cells. Studies with isolated proteins showed that MARK2 directly phosphorylates myosin II regulatory light chain, while its effects on MYPT1 phosphorylation are indirect. Using a mutant lacking the membrane-binding domain, we found that membrane association is required for focal adhesion targeting of MARK2, where it specifically enhances cell protrusion by promoting FAK phosphorylation and formation of focal adhesions oriented in the direction of migration to mediate directionally persistent cell motility. Together, our results define MARK2 as a master regulator of the actomyosin and microtubule cytoskeletal systems and focal adhesions to mediate directional cancer cell migration.

Drosophila nicotinic acetylcholine receptor subunits and their native interactions with insecticidal peptide toxins.

Drosophila nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels that represent a target for insecticides. Peptide neurotoxins are known to block nAChRs by binding to their target subunits, however, a better understanding of this mechanism is needed for effective insecticide design. To facilitate the analysis of nAChRs we used a CRISPR/Cas9 strategy to generate null alleles for all ten nAChR subunit genes in a common genetic background. We studied interactions of nAChR subunits with peptide neurotoxins by larval injections and styrene maleic acid lipid particles (SMALPs) pull-down assays. For the null alleles, we determined the effects of α-Bungarotoxin (α-Btx) and ω-Hexatoxin-Hv1a (Hv1a) administration, identifying potential receptor subunits implicated in the binding of these toxins. We employed pull-down assays to confirm α-Btx interactions with the Drosophila α5 (Dα5), Dα6, Dα7 subunits. Finally, we report the localisation of fluorescent tagged endogenous Dα6 during Drosophila CNS development. Taken together, this study elucidates native Drosophila nAChR subunit interactions with insecticidal peptide toxins and provides a resource for the in vivo analysis of insect nAChRs.

Desmosome Dysregulation and MLC Phosphorylation Contribute to Loss of Barrier Integrity in DRA KO mice

DRA or SLC26A3 is the key transporter for chloride absorption in the mammalian intestine. Our recent studies demonstrated that DRA deficiency increased paracellular permeability and altered tight and adherens junction protein expression in mouse colon. However, the mechanisms underlying increased paracellular permeability and the role of intercellular junctional proteins (desmosomes) that play a critical role in the maintenance of intestinal barrier integrity in DRA KO mice are not well understood. Aim The current studies were undertaken to examine the role of desmosomes and Rho‐ROCK‐MLC phosphorylation pathway in colonic barrier integrity in DRA KO mice.MethodDRA KO and WT mice (M/F, 8‐10 weeks old) were used as an in‐vivo model. Protein expression was measured by immunoblotting and immunofluorescence, whereas mRNA expression was measured by QRT‐PCR and Rho A activity was examined utilizing the G‐LISA kit.ResultsOur results showed that the mRNA expression of desmosome proteins, desmoglein‐2 (DSG2) and desmocollin‐2 (DSC2) was significantly reduced (50‐70%, p&lt;0.05) in DRA KO colons compared to wild‐type mice. Similarly, DSG2 protein expression was also significantly downregulated in DRA KO mice colon (~ 50%, p&lt;0.05) as assessed by immunoblotting and immunostaining. We also examined the role of Rho‐ROCK‐MLC2 phosphorylation pathway in DRA KO mice. Interestingly, DRA KO mice colon showed a significant increase in Rho A protein expression (~5‐fold, p&lt;0.01) and Rho A activity (~ 3.5‐fold, p&lt;0.05) compared to WT. Furthermore, DRA KO mice also exhibited a significant decrease in ezrin phosphorylation (a downstream target of Rho A signaling) (~ 2‐fold, p&lt;0.05) compared to WT mice. In addition, another downstream target of the Rho A pathway, MYPT‐1 (Myosin Phosphatase Target Subunit 1), also showed a significant decrease (~ 60%, p&lt;0.05) in its protein expression in DRA KO mice. MYPT‐1 downregulation in DRA KO mice was associated with a significant increase in MLC‐2 phosphorylation (~ 2‐fold, p&lt;0.05), which may have contributed to barrier dysfunction in colon of DRA KO mice. Since, our recent studies showed microbial dysbiosis in DRA KO mice, it was of interest to examine the role of gut microbiome by co‐housing WT and KO mice for 4 weeks for microbial exchange. Interestingly, co‐housed DRA KO mice also showed a significant but lower increase in Rho A expression (~ 3‐fold, p&lt;0.05) and downregulation of MYPT‐1 expression (~ 60%, p&lt;0.05) compared to co‐housed WT mice indicating that the regulation of Rho A and MYPT‐1 expression was only partly dependent on microbial dysbiosis observed in DRA KO mice.ConclusionOur studies highlight the novel role of desmosome dysregulation and increased MLC phosphorylation in compromised colonic barrier integrity in DRA KO mice.

PP1cβ dephosphorylates cardiac myosin by MYPT‐dependent and independent mechanisms

In beating hearts, cardiac muscle myosin is phosphorylated at its regulatory light chain (RLC) at 0.4 mol phosphate/mol RLC. This level of constitutive phosphorylation is necessary for normal cardiac function, and is maintained by balanced activities of the dedicated cardiac muscle‐specific myosin light chain kinase (MLCK) and myosin light chain phosphatase (MLCP). The MLCP is best characterized in the smooth muscle, and is comprised of the regulatory myosin phosphatase target subunit MYPT1, a catalytic subunit PP1cβ, and an accessory subunit of unknown function M20. In smooth muscles in vivo, MYPT1 and PP1cβ co‐stabilize each other and are both necessary for normal smooth muscle contractions. In the cardiac muscle, the ubiquitously‐expressed MYPT1 and the striated muscle‐specific MYPT2 are both expressed in the cardiomyocyte, but the contributions to physiological regulation of cardiac myosin dephosphorylation by PP1cβ are unclear.Using a conditional knockout of PP1cβ, we tested the hypothesis that the main catalytic subunit for cardiac MLCP is PP1cβ, and that its activity toward phosphorylated cardiac RLC in vivo is dependent on regulation by striated muscle‐specific MYPT2. We measured the effects of the knockout on the expression levels of other regulators of cardiac RLC phosphorylation, and a cardiac myofibrillar phosphatase assay was developed to measure MYPT‐regulated and MYPT‐independent phosphatase activities toward phosphorylated cardiac myosin. We report that 1) PP1cβ is the main isoform expressed in the cardiac myocyte, 2) cardiac muscle pathogenesis in PP1cβ knockout animals involve upregulation of PP1cα and MYPT1 in activated myofibroblasts, 3) the protein stability of endogenous mouse cardiac MYPT1 and MYPT2 are not dependent on the expression of PP1cβ, and 4) phosphorylated cardiac myosin in intact myofibrillar preparations are dephosphorylated by both myosin‐targeted and soluble MYPT‐independent PP1cβ activities. These results contribute to defining properties of the cardiac MLCP in vivo.

NOS isoforms facilitate Ca2+‐cycling‐dependent and ‐independent cardiac contractility

Increasing biased G‐protein coupled receptor (GPCR) drugs are now under clinical investigation. More understanding of the biased β‐adrenergic receptor (β‐AR) signaling is urgently required for a better cardiovascular drug. Here we found that two nitric oxide synthase (NOS) isotypes, NOS1, and NOS3 coupled with β1ARs and transduce distinct β1AR‐cGMP signaling at sarcoplasmic reticulum and myofilament microdomain, respectively. Intriguingly, activation of NOS1 enhanced contractility and Ca2+ cycling, whereas NOS3 promoted contraction without affecting intracellular Ca2+. Quantitative proteomic revealed that NOS3 activation increased phosphorylation of myosin proteins including myosin binding protein C (MyBP‐C), myosin light chain kinase (MYLK) and myosin phosphatase target subunit 1 (MYPT1), to enhance contractility by Ca2+sensitization. Moreover, in heart failure, excessive adrenergic stimulation dissociated β1AR from NOS1 and impaired the NOS1‐cGMP signaling. Accordingly, stimulating NOS3 but NOS1 enhances systolic cardiac contraction in failing mice without rousing intracellular Ca2+. We propose NOS facilitate biased β1AR‐cGMP signaling via Ca2+‐dependent or independent mechanisms and define NOS3‐cGMP as specific therapeutic strategy targeting myofilament for heart failure.

Elucidating the Bitter Taste Signaling Paradox in Airway Smooth Muscle Relaxation

RATIONALEAirway smooth muscle (ASM) hypersensitivity and hypercontractility play a pivotal role in the pathophysiology of obstructive airway diseases such as asthma. Furthermore, over half of affected individuals are unable to reliably control these disorders using the current standard of care, β‐(adrenergic) agonists. Previously, our group discovered the expression of a novel group of G protein‐coupled receptors (GPCRs), type 2 taste receptors (TAS2Rs), in the human airway which evoke ASM relaxation. Previous work in our lab suggests that TAS2R agonists evoke relaxation in a G protein beta‐gamma subunit‐, phospholipase C beta‐ and calcium‐dependent manner. We hypothesized that the downstream molecular targets of contractile‐related signaling components are differentially regulated by TAS2Rs compared to other GPCRs. The goal of this study was to establish the molecular mechanism by which TAS2Rs induce ASM relaxation.METHODSWe employed a phosphoproteomic approach, involving dual‐mass spectrometry, to determine differences in the phosphorylation status of contractile‐related proteins in ASM following the stimulation of TAS2Rs and other GPCRs. Healthy human ASM cells were treated with the TAS2R agonist chloroquine or β‐agonist isoproterenol alone or in combination with the bronchoconstrictive agonist histamine to study the ability of each relaxant compound to attenuate the histamine‐mediated phosphorylation profile of contractile‐related proteins. These phosphoproteomic profiles were compared and a select set of targets were validated using western blot analysis.RESULTSOur phosphoproteomic data demonstrated that histamine stimulation results in increased phosphorylation of Ras homolog family member A (RhoA) guanine nucleotide exchange factor (ARHGEF) 12 and A kinase anchoring proteins (AKAP) 2 and 12, as well as decreased phosphorylation of RhoA GTPase‐activating protein (ARHGAP) 6. Furthermore, chloroquine treatment attenuated histamine‐induced phosphorylation of ARHGEF12 but not AKAP2 or AKAP12. Interestingly, isoproterenol attenuated histamine‐induced phosphorylation of AKAP2 and AKAP12 but not ARHGEF12. Validation studies using western blot analysis revealed chloroquine mediated inhibition of histamine‐induced RhoA activation and myosin phosphatase target subunit 1 (MYPT1) phosphorylation at the T853 residue, which was not observed with isoproterenol.CONCLUSIONOur findings were able to show that contractile‐related proteins are phosphorylated differentially by chloroquine and isoproterenol to elicit ASM relaxation. Furthermore, our studies strongly suggest the importance of RhoA and the T853 residue on MYPT1 as points of mechanistic divergence between TAS2R and other GPCR pathways. These findings provide further insight into the mechanism by which TAS2R signaling reduces airway contractility and its potential as a novel therapy for obstructive airway disease.

Ionizable Lipid Nanoparticles Enhanced the Synergistic Adjuvant Effect of CpG ODNs and QS21 in a Varicella Zoster Virus Glycoprotein E Subunit Vaccine.

Varicella zoster virus (VZV) causes two diseases: varicella upon primary infection and herpes zoster when latent viruses in the sensory ganglia reactivate. While varicella vaccines depend on humoral immunity to prevent VZV infection, cell-mediated immunity (CMI), which plays a therapeutic role in the control or elimination of reactivated VZV in infected cells, is decisive for zoster vaccine efficacy. As one of the most abundant glycoproteins of VZV, conserved glycoprotein E (gE) is essential for viral replication and transmission between ganglion cells, thus making it an ideal target subunit vaccine antigen; gE has been successfully used in the herpes zoster vaccine ShingrixTM on the market. In this report, we found that ionizable lipid nanoparticles (LNPs) approved by the Food and Drug Administration (FDA) as vectors for coronavirus disease 2019 (COVID-19) mRNA vaccines could enhance the synergistic adjuvant effect of CpG oligodeoxynucleotides (CpG ODNs) and QS21 on VZV-gE, affecting both humoral immunity and CMI. Vaccines made with these LNPs showed promise as varicella vaccines without a potential risk of herpes zoster, which identifies them as a novel type of herpes zoster vaccine similar to ShingrixTM. All of the components in this LNP-CpG-QS21 adjuvant system were proven to be safe after mass vaccination, and the high proportion of cholesterol contained in the LNPs was helpful for limiting the cytotoxicity induced by QS21, which may lead to the development of a novel herpes zoster subunit vaccine for clinical application.

Tissue-specific expression of myosin phosphatase subunits and isoforms in smooth muscle of mice and humans.

Alternative splicing of exon24 (E24) of myosin phosphatase targeting subunit 1 (Mypt1) by setting sensitivity to nitric oxide (NO)/cGMP-mediated relaxation is a key determinant of smooth muscle function. Here we defined expression of myosin phosphatase (MP) subunits and isoforms by creation of new genetic mouse models, assay of human and mouse tissues, and query of public databases. A Mypt1-LacZ reporter mouse revealed that Mypt1 transcription is turned on early in development during smooth muscle differentiation. Mypt1 is not as tightly restricted in its expression as smooth muscle myosin heavy chain (Myh11) and its E6 splice variant. Mypt1 is enriched in mature smooth versus nonmuscle cells. The E24 splice variant and leucine zipper minus protein isoform that it encodes is enriched in phasic versus tonic smooth muscle. In the vascular system, E24 splicing increases as vessel size decreases. In the gastrointestinal system, E24 splicing is most predominant in smooth muscle of the small intestine. Tissue-specific expression of MP subunits and Mypt1 E24 splicing is conserved in humans, whereas a splice variant of the inhibitory subunit (CPI-17) is unique to humans. A Mypt1 E24 mini-gene splicing reporter mouse generated to define patterns of E24 splicing in smooth muscle cells (SMCs) dispersed throughout the organ systems was unsuccessful. In summary, expression of Mypt1 and splicing of E24 is part of the program of smooth muscle differentiation, is further enhanced in phasic smooth muscle, and is conserved in humans. Its low-level expression in nonmuscle cells may confound its measurement in tissue samples.

Short-term mechanisms activated by the nerve growth factor NGF to induce pulmonary arterial hyperreactivity

We have previously shown a pathophysiological role for NGF in pulmonary hypertension, particularly in pulmonary arterial (PA) hyperreactivity. Our experiments have suggested different mechanisms activated by NGF depending on a short–or a long-term PA treatment. The aim of the present study was to determine the mechanisms activated after a NGF short–term PA treatment (1 h) leading to PA hyperreactivity. Basal and agonist-induced calcium responses were evaluated in vitro in primary rat PA smooth muscle cells (rPASMC) using calcium imaging (Fura-2, Fluo-4), in the absence or presence of NGF (100 ng/ml, 1 h). Calcium sources involved in NGF-increased calcium responses were determined using endoplasmic reticulum calcium stores depleters (thapsigargin, 1 μM or cyclopiazonic acid, 10 μM), or a calcium–free extracellular medium. NGF–induced phosphorylation of myosin phosphatase target subunit 1 (MYPT1) was evaluated in vitro by Western blotting in primary human PA smooth muscle cells (hPASMC). Contractions of rat PA were induced ex vivo by endothelin-1 (ET-1, 10 -12 –10 -6 M) or phenylephrine (PHE, 10 -10 –10 -6 M) in the absence or presence of NGF (100 ng/ml, 1 h), with or without K252a (TrkA kinase inhibitor, 300 nM) or Y–27632 (Rho-associated protein kinase -ROCK-inhibitor, 10 μM). In vitro, NGF short-term treatment increases both basal and agonist-induced intracellular calcium responses in rPASMC, with endoplasmic reticulum being the main calcium source contributing to these effects. In addition, short–term treatment with NGF induced MYPT1 phosphorylation in hPASMC, involving a TrkA/ROCK-dependent pathway. Ex vivo, short-term treatment with NGF increased rat PA reactivity to PHE and ET–1. This effect was totally abolished after treatment with K252a or Y-27632. In conclusion, our results show that NGF can induce PA hyperreactivity through activation of its TrkA receptor, leading to both modulation of calcium intracellular responses and activation of ROCK-dependent calcium sensitization mechanisms. Such mechanisms may therefore contribute to NGF-dependent PA hyperreactivity in pulmonary hypertension.

Phosphodiesterase 4D promotes angiotensin II-induced hypertension in mice via smooth muscle cell contraction

Hypertension is a common chronic disease, which leads to cardio-cerebrovascular diseases, and its prevalence is increasing. The cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) pathway participates in multiple cardiovascular diseases. Phosphodiesterase (PDE) 4 has been shown to regulate PKA activity via cAMP specific hydrolysis. However, whether PDE4-cAMP-PKA pathway influences hypertension remains unknown. Herein, we reveal that PDE4D (one of PDE4 isoforms) expression is upregulated in the aortas of experimental hypertension induced by angiotensin II (Ang II). Furthermore, knockout of Pde4d in mouse smooth muscle cells (SMCs) attenuates Ang II-induced hypertension, arterial wall media thickening, vascular fibrosis and vasocontraction. Additionally, we find that PDE4D deficiency activates PKA-AMP-activated protein kinase (AMPK) signaling pathway to inhibit myosin phosphatase targeting subunit 1 (MYPT1)-myosin light chain (MLC) phosphorylation, relieving Ang II-induced SMC contraction in vitro and in vivo. Our results also indicate that rolipram, a PDE4 inhibitor, may be a potential drug for hypertension therapy.

Identification of the Kinase-Substrate Recognition Interface between MYPT1 and Rho-Kinase.

Protein kinases exert physiological functions through phosphorylating their specific substrates; however, the mode of kinase–substrate recognition is not fully understood. Rho-kinase is a Ser/Thr protein kinase that regulates cytoskeletal reorganization through phosphorylating myosin light chain (MLC) and the myosin phosphatase targeting subunit 1 (MYPT1) of MLC phosphatase (MLCP) and is involved in various diseases, due to its aberrant cellular contraction, morphology, and movement. Despite the importance of the prediction and identification of substrates and phosphorylation sites, understanding of the precise regularity in phosphorylation preference of Rho-kinase remains far from satisfactory. Here we analyzed the Rho-kinase–MYPT1 interaction, to understand the mode of Rho-kinase substrate recognition and found that the three short regions of MYPT1 close to phosphorylation sites (referred to as docking motifs (DMs); DM1 (DLQEAEKTIGRS), DM2 (KSQPKSIRERRRPR), and DM3 (RKARSRQAR)) are important for interactions with Rho-kinase. The phosphorylation levels of MYPT1 without DMs were reduced, and the effects were limited to the neighboring phosphorylation sites. We further demonstrated that the combination of pseudosubstrate (PS) and DM of MYPT1 (PS1 + DM3 and PS2 + DM2) serves as a potent inhibitor of Rho-kinase. The present information will be useful in identifying new substrates and developing selective Rho-kinase inhibitors.