Threonine Amino Acid Residues Research Articles

Enhancing intracellular delivery of protein kinase C beta II peptide inhibitor using myristic acid-trans-activator of transcription via N-terminus conjugation in isolated rat polymorphonuclear leukocytes

Introduction: Protein kinase C beta II (PKCβII) activation promotes polymorphonuclear (PMN) superoxide (SO) production by phosphorylating serine and threonine amino acid residues on NADPH oxidase (NOX-2). Previous studies have shown that cell permeable myristic acid-conjugated PKCβII inhibitor (myr-PKCβII-; SLNPEWNET) (20 μM) remarkably attenuated phorbol 12-myristate 13-acetate (PMA)-induced PMN SO release when compared to scrambled control peptide (myr-PKCβII- scram; WNPESLNTE), unconjugated peptides and nontreated controls by ~35%. This suggests an enhanced intracellular delivery of PKCβII-. Studies have also shown that SO release is attenuated via trans-activator of transcription-conjugated (Tat; YGRKKRRQRRR) NOX-2 inhibitor (Nox2ds-Tat) (80 μM) by ~37%. There have not been evaluations of Tat- or dual myr-Tat-conjugated PKCβII-. We hypothesize that dual myr-Tat-conjugation would enhance the intracellular delivery of PKCβII- and reduce SO release compared to myr-, Tat-, and myr-Tat-PKCβII- scram. Methods: This study focused on the effects of myr-Tat-PKCβII- on intracellular delivery compared to myr-PKCβII-, Tat -PKCβII-, and myr-Tat-PKCβII- scram, with 0.5% dimethyl sulfoxide (DMSO) vehicle as the control. Sprague-Dawley (SD) male rats (~400g) were anesthetized with isoflurane and given a 0.5% glycogen i.p. injection (16ml), and 16-18hrs later, PMNs were harvested from the peritoneal cavity and incubated for 15min at 37oC with 5μM myr-Tat-PKCβII-, myr-PKCβII-, Tat-PKCβII-, or myr-Tat-PKCβII- scram. PMN SO release was calculated spectrophotometrically by the change in absorbance at 550 nm over 390s via ferricytochrome c reduction after PMA stimulation (100nM). Data were analyzed with ANOVA Fisher’s PLSD post-hoc analysis. Results: Myr-Tat-PKCβII- (n=20, 0.338±0.024, p<0.05) and Myr-PKCβII- (n=8, 0.342±0.041, p<0.05) displayed significant attenuation of SO release by 28% and 27%, respectively, compared to 0.5% DMSO control (n=81, 0.470±0.013). Tat-PKCβII- (n=5, 0.404±0.049) showed attenuated SO release by 14% when compared to the vehicle control. Myr-Tat-PKCβII- scram (n=3, 0.542±0.081) showed an increase in SO release by 15% when compared to the vehicle control. Cell viability was > 85% in all groups. Conclusion: The results of the study suggest that intracellular delivery of PKCβII- cargo using myr-Tat dual conjugation is enhanced when compared to myr-, Tat-conjugated PKCβII-, and myr-Tat-PKCβII- scram. Future studies will utilize western blot analysis and immunohistochemistry to assess the translocation and activity of PKCβII- when conjugated with myr-Tat, myr-, or Tat- peptides. Funding: This study was funded by the National Heart, Lung & Blood Institute (1R43HL160338) SBIR phase I grant that was awarded to Young Therapeutics, LLC. Philadelphia College of Osteopathic Medicine, the Department of Biomedical Sciences, the Division of Research and the Center for Chronic Diseases of Aging. and Young Therapeutics, LLC. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Myristic Acid‐Trans‐Activator of Transcription Dual Conjugation Improves Intracellular Delivery of Protein Kinase C Beta II Peptide Inhibitor Cargo in Isolated Rat Polymorphonuclear Leukocytes

Protein kinase C beta II (PKCβII) activation promotes polymorphonuclear (PMN) superoxide (SO) production by phosphorylating serine and threonine amino acid residues on NADPH oxidase (NOX‐2). In previous studies, cell‐permeable myristic acid conjugated PKCβII inhibitor (myr‐PKCβII‐) significantly attenuated PMN SO release induced by phorbol 12‐myristate 13‐acetate (PMA), a diacylglycerol mimetic. Myr‐PKCβII‐ was determined to be superior to unconjugated peptides and nontreated controls, suggesting enhanced intracellular delivery of cargo. We hypothesize that the simple diffusion of myr‐conjugation combined with the endocytotic mechanism of trans‐activator of transcription (Tat) would optimize the intracellular delivery of PKCβII‐ cargo compared to myr‐conjugation alone.In this study, we tested the concentration‐dependent effects of a dual myr‐Tat conjugated PKCβII‐ (myr‐Tat‐PKCβII‐; N‐myr‐Tat‐CC‐SLNPEWNET) on intracellular delivery compared to myr‐PKCβII‐, scrambled myr‐Tat‐PKCβII‐ (myr‐Tat‐PKCβII‐ scram), unconjugated PKCβII‐, and 0.5% dimethyl sulfoxide (DMSO) vehicle control group. Rat PMNs were incubated for 15 min at 37°C with either unconjugated PKCβII‐ (20μM), myr‐Tat‐PKCβII‐ (2μM, 5μM, 7.5μM, 10μM, and 20μM), or myr‐Tat‐PKCβII‐scram (2μM, 5μM, 7.5μM, 10μM, and 20μM). PMN SO release was calculated by the change in absorbance at 550 nm over 390 sec via ferricytochrome c reduction after PMA stimulation (100nM). The efficacy of intracellular drug delivery was evaluated by the magnitude of PMA‐induced PMN SO release attenuation with the PKCβII‐ cargo. Data were analyzed with ANOVA Fisher’s PLSD post‐hoc analysis.Myr‐Tat‐PKCβII‐ 5μM (n=12, 0.392±0.04), 7.5μM (n=11, 0.397±0.05), 10μM (n=5, 0.211±0.05) and 20μM (n=5, 0.121±0.02) demonstrated a concentration‐dependent increase in intracellular delivery compared to DMSO vehicle control (n=84, 0.496±0.02, all p<0.05). Myr‐PKCβII‐ only significantly increased intracellular delivery at the 20μM concentration (n=27, 0.303±0.02, p<0.05) compared to DMSO vehicle control. Intracellular delivery of myr‐Tat‐PKCβII‐ 2μM (n=10, 0.436±0.06) and all concentrations of myr‐Tat‐PKCβII‐scram were not significantly different from DMSO vehicle controls.Results suggest that myr‐Tat dual conjugation is superior to myr‐conjugation alone at intracellular delivery of cell impermeant cargo. Future studies will investigate the concentration‐dependent effects of PKCβII‐ peptide conjugates on PMA‐induced PKCβII activity and translocation to membrane targets, such as NOX‐2, using immunocytochemistry and western blot analysis.

The novel potent GSK3 inhibitor AF3581 reverts fragile X syndrome phenotype.

Glycogen-synthase kinase 3 (GSK3) is a kinase mediating phosphorylation on serine and threonine amino acid residues of several target molecules. The enzyme is involved in the regulation of many cellular processes and aberrant activity of GSK3 has been linked to several disease conditions such as fragile X syndrome (FXS). Recent evidences demonstrating an increased activity of GSK3 in murine models of FXS, suggest that dysregulation/hyperactivation of the GSK3 path should contribute to FXS development. A likely possibility could be that in FXS there is a functional impairment of the upstream inhibitory input over GSK3 thus making overactive the kinase. Since GSK3 signaling is a central regulatory node for critical neurodevelopmental pathways, understanding the contribution of GSK3 dysregulation to FXS, may provide novel targets for therapeutic interventions for this disease. In this study we used AF3581, a potent GSK3 inhibitor that we recently discovered, in an in vivo FXS mouse model to elucidate the crucial role of GSK3 in specific behavioral patterns (locomotor activity, sensorimotor gating and social behavior) associated with this disease. All the behavioral alterations manifested by Fmr1 knockout mice were reverted after a chronic treatment with our GSK3 inhibitor, confirming the importance of this pathway as a therapeutic target.

Synthesis and Enhanced Capture Properties of a New BioMOF@SWCNT‐BP: Recovery of the Endangered Rare‐Earth Elements from Aqueous Systems

AbstractHuman society is facing—among other environmental threats—an enormous challenge due to human activities. The extensive use of high‐tech devices and electronics equipment in the daily life makes, among others, rare‐earth elements (REEs) recovery from secondary sources highly required. Here, a novel bioMOF‐based single‐walled carbon nanotube buckypaper (SWCNTBP) is presented as a new and efficient composite material (BioMOF@SWCNT‐BP). The flexible and highly crystalline metal–organic framework (MOF), prepared from the natural amino acid L‐threonine, has been homogeneously dispersed within the tangled net of a self‐standing SWCNT‐BP for lanthanides recovery from water. This MOF‐carbon‐based membrane exhibits high efficiency, either in static or dynamic regimes, in the recovery of lanthanides from aqueous streams outperforming the state‐of‐the‐art. The capture performances of BPs are successfully improved after incorporation of such MOF featuring hexagonal functional channels decorated with the threonine amino acid residues, pointing toward the accessible void spaces, which boosts the capture properties of the final membrane, providing the adaptable functional environment to interact with lanthanides. This material's preparation presents also a potential for large‐scale applications with a potential benefit on natural aquatic ecosystems as well. It is highly demanded because REEs from non‐recycled waste materials are potential pollutants for surface waters.

The mood stabilizing properties of AF3581, a novel potent GSK-3β inhibitor

The mood stabilizing properties of AF3581, a novel potent GSK-3β inhibitor

Abstract 1131: O-GlcNAc transferase inhibition in breast cancer cells

Abstract O-linked-N-acetylglucosamination (O-GlcNAcylation) is a post-translational modification that occurs on serine and threonine amino acid residues of the intracellular proteins. O-GlcNAcylation of numerous targets is catalyzed by a single enzyme - O-GlcNAc-transferase (OGT). O-GlcNAcylation impacts protein activation and stability thereby regulating several key biological functions, and is heavily involved in cancer development and progression. OGT expression and total protein O-GlcNAcylation are elevated in many cancers compared to non-malignant adjacent tissues. In breast cancer, this increase also has a positive correlation with the tumor grade suggesting a possible link to metastasis and disease progression. Here we investigated the effects of OGT inhibition in two triple-negative (TNBC) and two receptor-positive luminal breast cancer cell lines. Treatment of cells with an OGT inhibitor as well as OGT knockdown led to a strong decrease in viability and proliferation of the TNBC cells, but significantly less so in the luminal receptor-positive cell lines. This differential response was evaluated using analysis of apoptosis, cell cycle, gene expression and a reverse-phase antibody-based protein array (RPPA). We found that cell cycle progression was affected by OGT inhibition. In addition, proteomics data pointed towards the transcription factor hairy and enhancer of split-1 (HES1) as a possible mediator of the cytotoxicity observed in the TNBC cell lines. We currently work to elucidate the molecular mechanisms of HES1 regulation by OGT and its effect on TNBC cell survival and apoptosis. In conclusion, OGT inhibition has a pronounced cytotoxic effect on the TNBC cells and may have some potential for therapeutic use in the future. Citation Format: Anna Barkovskaya, Lina Prasmickaite, Damien Y. Duveau, Ian G. Mills, Gunhild M. Mælandsmo, Siver A. Moestue, Harri M. Itkonen. O-GlcNAc transferase inhibition in breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1131. doi:10.1158/1538-7445.AM2017-1131

NDRG2 promotes myoblast proliferation and caspase 3/7 activities during differentiation, and attenuates hydrogen peroxide – But not palmitate-induced toxicity

The function of the stress-responsive N-myc downstream-regulated gene 2 (NDRG2) in the control of myoblast growth, and the amino acids contributing to its function, are not well characterized. Here, we investigated the effect of increased NDRG2 levels on the proliferation, differentiation and apoptosis in skeletal muscle cells under basal and stress conditions. NDRG2 overexpression increased C2C12 myoblast proliferation and the expression of positive cell cycle regulators, cdk2, cyclin B and cyclin D, and phosphorylation of Rb, while the serine/threonine-deficient NDRG2, 3A-NDRG2, had less effect. The onset of differentiation was enhanced by NDRG2 as determined through the myogenic regulatory factor expression profiles and myocyte fusion index. However, the overall level of differentiation in myotubes was not different. While NDRG2 up-regulated caspase 3/7 activities during differentiation, no increase in apoptosis was measured by TUNEL assay or through cleavage of caspase 3 and PARP proteins. During H2O2 treatment to induce oxidative stress, NDRG2 helped protect against the loss of proliferation and ER stress as measured by GRP78 expression with 3A-NDRG2 displaying less protection. NDRG2 also attenuated apoptosis by reducing cleavage of PARP and caspase 3 and expression of pro-apoptotic Bax while enhancing the pro-survival Bcl-2 and Bcl-xL levels. In contrast, Mcl-1 was not altered, and NDRG2 did not protect against palmitate-induced lipotoxicity. Our findings show that NDRG2 overexpression increases myoblast proliferation and caspase 3/7 activities without increasing overall differentiation. Furthermore, NDRG2 attenuates H2O2-induced oxidative stress and specific serine and threonine amino acid residues appear to contribute to its function in muscle cells.

Insulin Resistance: A Bridge between T2DM and Alzheimer’s Disease

T2DM is caused by insulin resistance in the tissues, no longer able to respond to the hormone action. It is most frequently associated with aging, a family history of diabetes, obesity, and failure of exercise.The insulin, ahormone produced by the beta-cells of the pancreas, is the key biomolecule for the regulation of carbohydrate and lipid metabolism. Although its action in body organs mainly concerns the glucose homeostasis, in Central Nervous System insulin performs several functions such as regulation of glucose metabolism, food intake and body weight, fertility and reproduction [1] and others not yet completely known. In particular, the high density of insulin receptors in the hippocampus and cerebral cortex regions has suggested its participation in learning and memory process. The administration of insulin to both humans and animal models has induced an enhancement of the memory function [2] and the treatment with insulin has given in several animal models beneficial effects to prevent memory loss after ischemia episodes whereas no effects are observed with glucose alone [3]. Insulin is also involved in the synaptic plasticity, for example, it as been show that insulin allows the long-lasting enhancement of GABA receptormediated synaptic transmission [4] and promote the internalization of AMPA receptors from the neuron synaptic membrane causing a long-term depression (LTD) of excitatory synaptic transmission in the hippocampus and cerebellum [5,6]. LTD is a process that, together with the opposite one, long-term potentiation has a great relevance for brain information storage and improvement of neurons links during development [7]. Furthermore, insulin receptor signaling regulates the maintenance of synapses and contributes to experience-dependent structural plasticity that is necessary for the recruitment of neurons into brain circuits [8]. Moreover, some studies suggest that insulin participates in neuronal differentiation of postnatal neural stem cell [9] and their culturing with both insulin and insulin-like growth factor (GF-1) causes a greater production of neurons during differentiation compared to culturesstimulated by IGF-1 alone [10]. Insulin also avoids the necrosis of rat embryonic neurons cultured in a serum-free medium; in fact the protein was capable to restore the cell viability by activation of Protein Kinase C, having the crucial role of controlling other proteins through the phosphorylation of their serine and threonine amino acid residues; on the contrary, insulinlike growth factor addition had no effect [11]. Clearly, in the insulin resistance state, these functions are impaired.

Tau Mislocalization to Dendritic Spines Mediates Synaptic Dysfunction Independently of Neurodegeneration

The microtubule-associated protein tau accumulates in Alzheimer's and other fatal dementias, which manifest when forebrain neurons die. Recent advances in understanding these disorders indicate that brain dysfunction precedes neurodegeneration, but the role of tau is unclear. Here, we show that early tau-related deficits develop not from the loss of synapses or neurons, but rather as a result of synaptic abnormalities caused by the accumulation of hyperphosphorylated tau within intact dendritic spines, where it disrupts synaptic function by impairing glutamate receptor trafficking or synaptic anchoring. Mutagenesis of 14 disease-associated serine and threonine amino acid residues to create pseudohyperphosphorylated tau caused tau mislocalization while creation of phosphorylation-deficient tau blocked the mistargeting of tau to dendritic spines. Thus, tau phosphorylation plays a critical role in mediating tau mislocalization and subsequent synaptic impairment. These data establish that the locus of early synaptic malfunction caused by tau resides in dendritic spines.

Assessment of the Transferability of a Protein Force Field for the Simulation of Peptide-Surface Interactions

In order to evaluate the transferability of existing empirical force fields for all-atom molecular simulations of protein adsorption behavior, we have developed and applied a method to calculate the adsorption free energy (DeltaG(ads)) of model peptides on functionalized surfaces for comparison with available experimental data. Simulations were conducted using the CHARMM program and force field using a host-guest peptide with the sequence TGTG-X-GTGT (where G and T are glycine and threonine amino acid residues, respectively, with X representing valine, threonine, aspartic acid, phenylalanine or lysine) over nine different functionalized alkanethiol self-assembled monolayer (SAM) surfaces with explicitly represented solvent. DeltaG(ads) was calculated using biased-energy replica exchange molecular dynamics to adequately sample the conformational states of the system. The simulation results showed that the CHARMM force-field was able to represent DeltaG(ads) within 1 kcal/mol of the experimental values for most systems, while deviations as large as 4 kcal/mol were found for others. In particular, the simulations reveal that CHARMM underestimates the strength of adsorption on the hydrophobic and positively charged amine surfaces. These results clearly show that improvements in force field parameterization are needed in order to accurately represent interactions between amino acid residues and functional groups of a surface and they provide a means for force field evaluation and modification for the eventual development and validation of an interfacial force field for the accurate simulation of protein adsorption behavior.

Benchmark Experimental Data Set and Assessment of Adsorption Free Energy for Peptide−Surface Interactions

With the increasing interest in protein adsorption in fields ranging from bionanotechnology to biomedical engineering, there is a growing need to understand protein-surface interactions at a fundamental level, such as the interaction between individual amino acid residues of a protein and functional groups presented by a surface. However, relatively little data are available that experimentally provide a quantitative, comparative measure of these types of interactions. To address this deficiency, the objective of this study was to generate a database of experimentally measured standard state adsorption free energy (DeltaGoads) values for a wide variety of amino acid residue-surface interactions using a host-guest peptide and alkanethiol self-assembled monolayers (SAMs) with polymer-like functionality as the model system. The host-guest amino acid sequence was synthesized in the form of TGTG-X-GTGT, where G and T are glycine and threonine amino acid residues and X represents a variable residue. In this paper, we report DeltaGoads values for the adsorption of 12 different types of the host-guest peptides on a set of nine different SAM surfaces, for a total of 108 peptide-surface systems. The DeltaGoads values for these 108 peptide-surface combinations show clear trends in adsorption behavior that are dependent on both peptide composition and surface chemistry. These data provide a benchmark experimental data set from which fundamental interactions that govern peptide and protein adsorption behavior can be better understood and compared.

Apoptosis signaling by the novel compound 3-Cl-AHPC involves increased EGFR proteolysis and accompanying decreased phosphatidylinositol 3-kinase and AKT kinase activities.

The threonine and serine protein kinase AKT plays a major role in inhibiting apoptosis in a number of malignant cell types including prostate and breast carcinoma. Activation of AKT is a complex process involving translocation to the plasma membrane and phosphorylation of serine and threonine amino-acid residues. We now report that the novel compound 4-[3-(1-adamantyl)-4-hydroxyphenyl]-3-chlorocinnamic acid (3-Cl-AHPC), induces apoptosis in breast and prostate carcinoma cells and inhibits AKT activity in these cells. Overexpression of a constitutively activated AKT inhibits 3-Cl-AHPC-mediated apoptosis. Decrease in AKT activity occurs through 3-Cl-AHPC inhibition of phosphatidylinositol 3 kinase (PI3-K) activity. 3-Cl-AHPC inhibits PI3-K activity by enhancing epidermal growth factor receptor (EGFR) proteolysis and thus inhibiting EGFR association with the p85 subunit of PI3-K. 3-Cl-AHPC-mediated decrease in PI3-K activity results in the reduced synthesis of phosphatidylinositol 3,4 bisphosphate and phosphatidylinositol 3,4,5 triphosphate with the subsequent inhibition of integrin-linked kinase activity and serine-473 phosphorylation of AKT. Overexpression of EGFR results in increased AKT activity and inhibition of 3-Cl-AHPC-mediated decrease in AKT activation, AKT activity and 3-Cl-AHPC-mediated apoptosis. Inhibition of AKT activity by this compound results in the inability of AKT to phosphorylate and inactivate the proapoptotic forkhead transcription factor.

Green fluorescent protein-based protein kinase biosensor substrates.

AbstractProtein kinases (PKs) are a family of enzymes that catalyze the transfer of γ-phosphate from adenosine triphosphate (ATP) to tyrosine, serine, or threonine amino acid residues of substrate proteins. Phosphorylation alters the enzymatic activity, binding capability, or cellular localization of the substrate protein, as a means to relay environmental signals, such as the extracellular matrix, antigens, insulin, and growth factors (1). Following the discovery of protein phosphorylation as a mechanism of signal transduction, the discovery of the v-src and v-abl oncogenes (2,3), and the realization that PKs are an immense superfamily of proteins (2.1% of Caenor elegans genes are PKs); PKs have moved to center stage in the field of signal transduction. Because of their centrality in cell signaling, PKs have also become attractive therapeutic targets for such diverse diseases as diabetes and cancer (4).KeywordsGreen Fluorescent ProteinKinase AssayCalf Intestinal Alkaline PhosphatasePhosphorylation SequenceGreen Fluorescent Protein ConstructThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.