Common Intracellular Signaling Pathways Research Articles

Systematic pan-cancer analysis identifies RALA as a tumor targeting immune therapeutic and prognostic marker.

RALA is a member of the small GTPase Ras superfamily and has been shown to play a role in promoting cell proliferation and migration in most tumors, and increase the resistance of anticancer drugs such as imatinib and cisplatin. Although many literatures have studied the cancer-promoting mechanism of RALA, there is a lack of relevant pan-cancer analysis. This study systematically analyzed the differential expression and mutation of RALA in pan-cancer, including different tissues and cancer cell lines, and studied the prognosis and immune infiltration associated with RALA in various cancers. Next, based on the genes co-expressed with RALA in pan-cancer, we selected 241 genes with high correlation for enrichment analysis. In terms of pan-cancer, we also analyzed the protein-protein interaction pathway of RALA and the application of small molecule drug Guanosine-5'-Diphosphate. We screened hepatocellular cancer (HCC) to further study RALA. The results indicated that RALA was highly expressed in most cancers. RALA was significantly correlated with the infiltration of B cells and macrophages, as well as the expression of immune checkpoint molecules such as CD274, CTLA4, HAVCR2 and LAG3, suggesting that RALA can be used as a kind of new pan-cancer immune marker. The main functions of 241 genes are mitosis and protein localization to nucleosome, which are related to cell cycle. For HCC, the results displayed that RALA was positively correlated with common intracellular signaling pathways such as angiogenesis and apoptosis. In summary, RALA was closely related to the clinical prognosis and immune infiltration of various tumors, and RALA was expected to become a broad-spectrum molecular immune therapeutic target and prognostic marker for pan-cancer.

Pick the best of both glucose and lipid metabolism.

Isthmin-1 is an adipokine that has a potent glucose-lowering effect by stimulating a common intracellular signaling pathway with insulin through a distinct receptor and has an inhibitory effect on lipogenesis in the liver, whereas insulin has the opposite effect. Isthmin-1 is expected to have clinical benefits in the treatment of diabetes.

Transcriptomic and functional proteomics analyses to unveil the common and unique pathway(s) of neuritogenesis induced by Russell’s viper venom nerve growth factor in rat pheochromocytoma neuronal cells

ABSTRACT Background : The snake venom nerve growth factor (NGF)-induced signal transduction mechanism has never been explored. Research design and methods : Homology modeling and molecular dynamic studies of the interaction between Russell’s viper venom NGF (RVV-NGFa) and mammalian tropomyosin-receptor kinase A (TrkA) was done by computational analysis. Transcriptomic and quantitative tandem mass spectrometry analyses determined the expression of intracellular genes and proteins, respectively, in RVV-NGFa-treated PC-12 neuronal cells. Small synthetic inhibitors of the signal transduction pathways were used to validate the major signaling cascades of neuritogenesis by RVV-NGFa. Results : A comparative computational analysis predicted the binding of RVV-NGFa, mouse 2.5S-NGF (conventional neurotrophin), and Nn-α-elapitoxin-1 (non-conventional neurotrophin) to different domains of the TrkA receptor in PC-12 cells. The transcriptomic and quantitative proteomic analyses in unison showed differential expressions of common and unique genes and intracellular proteins, respectively, in RVV-NGFa-treated cells compared to control (untreated) mouse 2.5S-NGF and Nn-α-elapitoxin-1-treated PC-12 cells. The RVV-NGFa primarily triggered the mitogen-activated protein kinase-1 (MAPK1) signaling pathway for inducing neuritogenesis; however, 36 pathways of neuritogenesis were uniquely expressed in RVV-NGFa-treated PC-12 cells compared to mouse 2.5S NGF or Nn-α-elapitoxin-1 treated cells. Conclusion : The common and unique intracellular signaling pathways of neuritogenesis by classical and non-classical neurotrophins were identified.

Cap-independent translation: A shared mechanism for lifespan extension by rapamycin, acarbose, and 17α-estradiol.

We hypothesized that rapamycin (Rapa), acarbose (ACA), which both increase mouse lifespan, and 17α‐estradiol, which increases lifespan in males (17aE2) all share common intracellular signaling pathways with long‐lived Snell dwarf, PAPPA‐KO, and Ghr−/− mice. The long‐lived mutant mice exhibit reduction in mTORC1 activity, declines in cap‐dependent mRNA translation, and increases in cap‐independent translation (CIT). Here, we report that Rapa and ACA prevent age‐related declines in CIT target proteins in both sexes, while 17aE2 has the same effect only in males, suggesting increases in CIT. mTORC1 activity showed the reciprocal pattern, with age‐related increases blocked by Rapa, ACA, and 17aE2 (in males only). METTL3, required for addition of 6‐methyl‐adenosine to mRNA and thus a trigger for CIT, also showed an age‐dependent increase blunted by Rapa, ACA, and 17aE2 (in males). Diminution of mTORC1 activity and increases in CIT‐dependent proteins may represent a shared pathway for both long‐lived‐mutant mice and drug‐induced lifespan extension in mice.

EMS1 and BRI1 control separate biological processes via extracellular domain diversity and intracellular domain conservation

In flowering plants, EMS1 (Excess Microsporocytes 1) perceives TPD1 (Tapetum Determinant 1) to specify tapeta, the last somatic cell layer nurturing pollen development. However, the signaling components downstream of EMS1 are relatively unknown. Here, we use a molecular complementation approach to investigate the downstream components in EMS1 signaling. We show that the EMS1 intracellular domain is functionally interchangeable with that of the brassinosteroid receptor BRI1 (Brassinosteroid Insensitive 1). Furthermore, expressing EMS1 together with TPD1 in the BRI1 expression domain could partially rescue bri1 phenotypes, and led to the dephosphorylation of BES1, a hallmark of active BRI1 signaling. Conversely, expressing BRI1 in the EMS1 expression domain could partially rescue ems1 phenotypes. We further show that PpEMS1 and PpTPD1 from the early land plant Physcomitrella patens could completely rescue ems1 and tpd1 phenotypes, respectively. We propose that EMS1 and BRI1 have evolved distinct extracellular domains to control different biological processes but can act via a common intracellular signaling pathway.

Propranolol inhibits catecholestrogen-induced human endometrial stromal cell survival mediated by p38 MAPK signaling: potential therapy for endometriosis

Catecholestrogens (CCEs), 2-Hydroxyestradiol (OHE2) and 4-OHE2, are biologically active metabolites of 17β-estradiol (E2). Studies indicate that local increases in E2 production as well as aberrant expression of E2 metabolizing enzymes enhance local generation of CCEs in women with endometriosis. CCEs have low binding affinity to estrogen receptors whereas CCEs display high binding affinity to β2-adrenergic receptor (AR), which induce uterine endothelial cell proliferation during gestation. Our recent data demonstrated β2-AR expression in eutopic and ectopic endometrial tissue. In addition, binding of CCEs to β-AR enhances human endometrial stromal cell (HESC) viability, suggesting contribution of CCEs to the pathogenesis of endometriosis. Thus, we tested the hypothesis that the mechanism of CCE-enhanced HESC viability involves alterations in either proliferation or apoptosis mediated by β-AR-induced common intracellular signaling pathways, i.e. AKT, MAPK and/or NFκB. BrdU, Apoptotic Cell Detection ELISA, q-PCR, Western blot and XTT analyses were performed on cultured HESCs derived from endometrial biopsies. Cultured HESCs treated with 10-8 M E2 or 2-OHE2 or 4-OHE2 were measured by BrdU for proliferation and ELISA for apoptosis (n=3 with quadruplicate). Total RNA from cultured HESCs was isolated and pro-apoptotic, anti-apoptotic, and proliferation markers were evaluated by q-PCR (n=5 with duplicate). Total and phosphorylated AKT, p38 and ERK1/2 MAPKs, and NFκB levels were detected in lysates of cultured HESCs (n=3 with triplicate) treated for 10 min with vehicle (control) or 10-8 M E2 or 2-OHE2 or 4-OHE2 ± 2x10-5 M non-specific β-antagonist (propranolol). Subsequently, XTT assays were conducted with p38 MAPK inhibitor to assess the role of p38 MAPK on CCE-induced HESC viability (n=4 with triplicate). Results were analyzed by One-way ANOVA and post hoc Tukey test. An increased HESC proliferation index by E2 and 4-OHE2 (P<0.05 and P<0.05, respectively) and decreased apoptosis were detected in HESCs treated with 2-OHE2 and 4-OHE2 vs. control (P<0.01 and P<0.01, respectively). Analysis of apoptotic markers by q-PCR revealed a significant decrease in Bax mRNA expression in response to 2-OHE2 treatment vs. control (P<0.01). Among the several intracellular signaling cascades analyzed, only phosphorylation levels of p38 MAPK were increased by either treatment with 2-OHE2 or 4-OHE2 (P<0.05 and P<0.05 vs. control, respectively), but not with E2. β-AR antagonism with propranolol mitigated this increased phosphorylation in p38 MAPK levels (P<0.05 and P<0.01, respectively) and inhibition of p38 MAPK by SB203580 blocked CCE-induced HESC survival (P<0.05 and P<0.001, respectively). These data indicate that induction of endometrial stromal cell viability by CCE-β-AR interactions results from an imbalance in both proliferation and anti-apoptotic mechanisms and is specifically mediated by the activation of p38 MAPK signaling. These data also suggest that inhibition of β2-ARs with propranolol may be a novel treatment option in endometriosis.

Vascular Anomalies Caused by Abnormal Signaling within Endothelial Cells: Targets for Novel Therapies.

Vascular anomalies arise as a consequence of improper development and maintenance of the vasculature. Our knowledge on the pathophysiological bases of vascular anomalies has skyrocketed during the past 5 years. It is becoming clear that common intracellular signaling pathways are often activated by mutations, causing endothelial cell dysfunction. These mutations cause hyperactivation of two major intracellular signaling pathways that may be controlled by inhibitors developed for cancer treatment. Although we do not know yet all the downstream effects, it has become evident that normalization of the abnormal signaling is an interesting target for therapy. This is a major paradigm change, as developmental malformations were considered to be inert to any molecular treatment.

Osteoimmunology: memorandum for rheumatologists.

Rapid progress has been made in exploring the connections between the skeletal system and the immune system over the past decade. Bone tissue forms developmental niches for hematopoietic stem cells, and activated immune cells are involved in bone metabolism regulation and are potent mediators of osteoporosis and bone erosion under pathological conditions. The interdisciplinary field of osteoimmunology has emerged to pool the knowledge of the interdependence of these two systems, including the shared ligands and receptors, their crosstalk and interaction, and common intracellular signaling pathways with bidirectional influence. The receptor activator of nuclear factor-kappa B (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) triad is the key vinculum, with multifaceted potency, being not only essential for osteoclastogenesis but also critical for lymph node organogenesis and lymphopoiesis as well as for immune regulation. In this review, we summarize the progress in this area, focusing on those aspects of interest concerning rheumatic diseases.

Leptin influences the excitability of area postrema neurons.

The area postrema (AP) is a circumventricular organ with important roles in central autonomic regulation. This medullary structure has been shown to express the leptin receptor and has been suggested to have a role in modulating peripheral signals, indicating energy status. Using RT-PCR, we have confirmed the presence of mRNA for the leptin receptor, ObRb, in AP, and whole cell current-clamp recordings from dissociated AP neurons demonstrated that leptin influenced the excitability of 51% (42/82) of AP neurons. The majority of responsive neurons (62%) exhibited a depolarization (5.3 ± 0.7 mV), while the remaining affected cells (16/42) demonstrated hyperpolarizing effects (-5.96 ± 0.95 mV). Amylin was found to influence the same population of AP neurons. To elucidate the mechanism(s) of leptin and amylin actions in the AP, we used fluorescence resonance energy transfer (FRET) to determine the effect of these peptides on cAMP levels in single AP neurons. Leptin and amylin were found to elevate cAMP levels in the same dissociated AP neurons (leptin: % total FRET response 25.3 ± 4.9, n = 14; amylin: % total FRET response 21.7 ± 3.1, n = 13). When leptin and amylin were coapplied, % total FRET response rose to 53.0 ± 8.3 (n = 6). The demonstration that leptin and amylin influence a subpopulation of AP neurons and that these two signaling molecules have additive effects on single AP neurons to increase cAMP, supports a role for the AP as a central nervous system location at which these circulating signals may act through common intracellular signaling pathways to influence central control of energy balance.

The molecular pathogenesis of B-cell non-Hodgkin lymphoma.

The B-cell non-Hodgkin lymphomas (B-NHL) are a diverse group of haematological malignancies which arise from the mature B-lymphocyte compartment. Recently, our understanding of the molecular pathogenesis of these disorders has greatly increased due to technological advances such as high-throughput DNA sequencing techniques. A paradigm of B-NHL pathogenesis has emerged where the normal genetic processes that are central to generating B-cell receptor diversity (somatic hypermutation and class switch/VDJ recombination) also drive the genesis of large-scale, chromosomal-level genetic lesions and smaller-scale gene-level mutations to produce the malignant phenotypes observed. Whilst a significant degree of genetic heterogeneity exists within each B-NHL subtype, the genetic lesions present within each subtype show a degree of convergence on common intracellular signalling, epigenetic and cell cycle pathways. This convergence gives an insight into the key oncogenic drivers of specific B-NHL subtypes and potential targets for therapeutic intervention. This review covers the current understanding of the causative genetic processes of B-NHL, the associated driving molecular lesions and the implications of these findings for the treatment of this group of disorders.

Aspirin inhibits cell viability and mTOR downstream signaling in gastroenteropancreatic and bronchopulmonary neuroendocrine tumor cells.

To investigate the effect of aspirin on neuroendocrine tumor (NET) cell growth and signaling in vitro. Human pancreatic BON1, bronchopulmonary NCI-H727 and midgut GOT1 neuroendocrine tumor cells were treated with different concentrations of aspirin (from 0.001 to 5 mmol/L), and the resulting effects on metabolic activity/cell proliferation were measured using cell proliferation assays and SYBR-DNA-labeling after 72, 144 and 216 h of incubation. The effects of aspirin on the expression and phosphorylation of several critical proteins that are involved in the most common intracellular growth factor signaling pathways (especially Akt protein kinase B) and mammalian target of rapamycin (mTOR) were determined by Western blot analyses. Propidium iodide staining and flow cytometry were used to evaluate changes in cell cycle distribution and apoptosis. Statistical analysis was performed using a 2-tailed Student's t-test to evaluate the proliferation assays and cell cycle analyses. The results are expressed as the mean ± SD of 3 or 4 independently performed experiments. Statistical significance was set at P < 0.05. Treatment with aspirin suppressed the viability/proliferation of BON1, NCI-H727 and GOT1 cells in a time- and dose-dependent manner. Significant effects were observed at starting doses of 0.5-1 mmol/L and peaked at 5 mmol/L. For instance, after treatment with 1 mmol/L aspirin for 144 h, the viability of pancreatic BON1 cells decreased to 66% ± 13% (P < 0.05), the viability of bronchopulmonary NCI-H727 cells decreased to 53% ± 8% (P < 0.01) and the viability of midgut GOT1 cells decreased to 89% ± 6% (P < 0.01). These effects were associated with a decreased entry into the S phase, the induction of the cyclin-dependent kinase inhibitor p21 and reduced expression of cyclin-dependent kinase 4 and cyclin D3. Aspirin suppressed mTOR downstream signaling, evidenced by the reduced phosphorylation of the mTOR substrates 4E binding protein 1, serine/threonine kinase P70S6K and S6 ribosomal protein and inhibited glycogen synthase kinase 3 activity. We observed the (compensatory) activation of tuberous sclerosis 2, the serine/threonine specific protein kinase AKT and extracellular signal-regulated kinases. Aspirin demonstrates promising anticancer properties for NETs in vitro. Further preclinical and clinical studies are needed.

Early sequence of events triggered by the interaction ofNeisseria meningitidiswith endothelial cells

Neisseria meningitidis is a bacterium responsible for severe sepsis and meningitis. Following type IV pilus-mediated adhesion to endothelial cells, bacteria proliferating on the cellular surface trigger a potent cellular response that enhances the ability of adhering bacteria to resist the mechanical forces generated by the blood flow. This response is characterized by the formation of numerous 100 nm wide membrane protrusions morphologically related to filopodia. Here, a high-resolution quantitative live-cell fluorescence microscopy procedure was designed and used to study this process. A farnesylated plasma membrane marker was first detected only a few seconds after bacterial contact, rapidly followed by actin cytoskeleton reorganization and bulk cytoplasm accumulation. The bacterial type IV pili-associated minor pilin PilV is necessary for the initiation of this cascade. Plasma membrane composition is a key factor as cholesterol depletion with methyl-β-cyclodextrin completely blocks the initiation of the cellular response. In contrast membrane deformation does not require the actin cytoskeleton. Strikingly, plasma membrane remodelling undermicrocolonies is also independent of common intracellular signalling pathways as cellular ATP depletion is not inhibitory. This study shows that bacteria-induced plasma membrane reorganization is a rapid event driven by a direct cross-talk between type IV pili and the plasma membrane rather than by the activation of an intracellular signalling pathway that would lead to actin remodelling.

Sex, sex steroids, and diabetic cardiomyopathy: making the case for experimental focus

More than three decades ago, the Framingham study revealed that cardiovascular risk is elevated for all diabetics and that this jeopardy is substantially accentuated for women in particular. Numerous studies have subsequently documented worsened cardiac outcomes for women. Given that estrogen and insulin exert major regulatory effects through common intracellular signaling pathways prominent in maintenance of cardiomyocyte function, a sex-hormone:diabetic-disease interaction is plausible. Underlying aspects of female cardiovascular pathophysiology that exaggerate cardiovascular diabetic risk may be identified, including increased vulnerability to coronary microvascular disease, age-dependent impairment of insulin-sensitivity, and differential susceptibility to hyperglycemia. Since Framingham, considerable progress has been made in the development of experimental models of diabetic disease states, including a diversity of genetic rodent models. Ample evidence indicates that animal models of both type 1 and 2 diabetes variably recapitulate aspects of diabetic cardiomyopathy including diastolic and systolic dysfunction, and cardiac structural pathology including fibrosis, loss of compliance, and in some instances ventricular hypertrophy. Perplexingly, little of this work has explored the relevance and mechanisms of sexual dimorphism in diabetic cardiomyopathy. Only a small number of experimental studies have addressed this question, yet the prospects for gaining important mechanistic insights from further experimental enquiry are considerable. The case for experimental interrogation of sex differences, and of sex steroid influences in the aetiology of diabetic cardiomyopathy, is particularly compelling-providing incentive for future investigation with ultimate therapeutic potential.

Cellular Signaling Crosstalk Between Multiple Receptors for Investigation of Pathophysiology in Multifactorial Diseases - What is Clinically-Relevant Crosstalk?

Recently, genomics and proteomics have been utilized as advanced tools for investigation of cellular signaling pathways and molecular interactions, and elucidated promiscuous networks composed of numerous interactions among pathways. However, some of these interactions are considered to be simply contributing to background 'noise' and others are as 'crosstalk' biologically-relevant to cellular physiology, leading to synergy effects more than additive responses in an entire organism. Effort is now required to determine which interactions truly contribute to final physiological output. A receptor is the prime example of connectors among the networks. It functions, not simply as a signaling gateway, but also as an active trader by forming inter-receptor dimers. Furthermore, various receptors can modulate the function of the other receptors by input to common intracellular signaling pathways, establishing functional crosstalk among networks. Our findings by combined analyses of gene polymorphisms of two separate genes present evidences that such is the case with human body in a clinical setting: 1) an integrated effect of epidermal growth factor receptor (EGFR) and protease activated receptor-1 (PAR-1) on susceptibility to airway hyperresponsiveness (AHR), and 2) a crosstalk effect between muscarinic acetylcholine receptor (mAChRs) and β(2) adrenoceptor (β(2)AR) on bronchodilatory response to anticholinergic agents in patients with COPD. These results indicate that these interactions are unlikely to be 'noise' but functionally-relevant 'crosstalk' in a human body. This review attempts to highlight the clinically-relevant 'crosstalk' paradigm in a human body which provides us a novel insight necessary to investigate pathophysiology in common multifactorial diseases and to develop new drugs.

At the leading edge of three-dimensional cell migration

Cells migrating on flat two-dimensional (2D) surfaces use actin polymerization to extend the leading edge of the plasma membrane during lamellipodia-based migration. This mode of migration is not universal; it represents only one of several mechanisms of cell motility in three-dimensional (3D) environments. The distinct modes of 3D migration are strongly dependent on the physical properties of the extracellular matrix, and they can be distinguished by the structure of the leading edge and the degree of matrix adhesion. How are these distinct modes of cell motility in 3D environments related to each other and regulated? Recent studies show that the same type of cell migrating in 3D extracellular matrix can switch between different leading edge structures. This mode-switching behavior, or plasticity, by a single cell suggests that the apparent diversity of motility mechanisms is integrated by a common intracellular signaling pathway that governs the mode of cell migration. In this Commentary, we propose that the mode of 3D cell migration is governed by a signaling axis involving cell-matrix adhesions, RhoA signaling and actomyosin contractility, and that this might represent a universal mechanism that controls 3D cell migration.

The inhibition of release by mGlu7 receptors is independent of the Ca 2+ channel type but associated to GABA B and adenosine A 1 receptors

Neurotransmitter release is inhibited by G-protein coupled receptors (GPCRs) through signalling pathways that are negatively coupled to Ca 2+ channels and adenylyl cyclase. Through Ca 2+ imaging and immunocytochemistry, we have recently shown that adenosine A 1, GABA B and the metabotropic glutamate type 7 receptors coexist in a subset of cerebrocortical nerve terminals. As these receptors inhibit glutamate release through common intracellular signalling pathways, their co-activation occluded each other responses. Here we have addressed whether the occlusion of receptor responses is restricted to the glutamate release mediated by N-type Ca 2+ channels by analysing this process in nerve terminals from mice lacking the α 1B subunit (Ca v 2.2) of these channels. We found that glutamate release from cerebrocortical nerve terminals without these channels, in which release relies exclusively on P/Q type Ca 2+ channels, is not modulated by mGlu7 receptors. Furthermore, there is no occlusion of the release inhibition by GABA B and adenosine A 1. Hence, in the cerebrocortical preparation, these three receptors only appear to coexist in N-type channel containing nerve terminals. In contrast, in hippocampal nerve terminals lacking this subunit, where mGlu7 receptors modulate glutamate release via P/Q type channels, the occlusion of inhibitory responses by co-stimulation of adenosine A 1, GABA B and mGlu7 receptors was observed. Thus, occlusion of the responses by the three GPCRs is independent of the Ca 2+ channel type but rather, it is associated to functional mGlu7 receptors.

Regulated ADAM10-dependent Ectodomain Shedding of γ-Protocadherin C3 Modulates Cell-Cell Adhesion

Gamma-protocadherins (Pcdh gamma) are type I transmembrane proteins, which are most notably expressed in the nervous system. They are enriched at synapses and involved in synapse formation, specification, and maintenance. In this study, we show that Pcdh gamma C3 and Pcdh gamma B4 are specifically cleaved within their ectodomains by the disintegrin and metalloprotease ADAM10. Analysis of ADAM10-deficient fibroblasts and embryos, inhibitor studies, as well as RNA interference-mediated down-regulation demonstrated that ADAM10 is not only responsible for the constitutive but also for the regulated shedding of these proteins in fibroblasts and in neuronal cells. In contrast to N-cadherin shedding, which was activated by N-methyl-D-aspartic acid receptor activation in neuronal cells, Pcdh gamma shedding was induced by alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid hydrate stimulation, suggesting differential regulation mechanisms of cadherin-mediated functions at synapses. Cell aggregation assays in the presence or absence of metalloprotease inhibitors strongly suggest that the ectodomain shedding events modulate the cell adhesion role of Pcdh gamma. The identification of ADAM10 as the protease responsible for constitutive and regulated Pcdh gamma shedding may therefore provide new insight into the regulation of Pcdh gamma functions.

Purification and in vitro characterization of adult canine olfactory ensheathing cells

Olfactory ensheathing cells (OECs) are known to promote neural repair under experimental conditions. The experimental focus has so far been almost entirely on rodent OECs (rOECs), and hence whether human OECs (humOECs) display similar properties is unclear. Studies on larger mammals as an "intermediate" model may be helpful for translating the experimental evidence gathered so far into novel therapeutic strategies. In the present study, we purified adult canine OECs (caOECs) from the olfactory bulb and analyzed their in vitro properties with respect to antigen expression, proliferation, and differentiation. Secondary caOECs shared the expression of marker molecules and the reactivity toward growth factors, with rOECs and humOECs. CaOECs were positively immunostained for the low affinity neurotrophin receptor p75, GFAP, and O4 and proliferated in response to fibroblast growth factor-2 and heregulin-1beta. No decline in proliferation was noted at higher passages (>8). The effects of forskolin, which neither increased proliferation nor stimulated the expression of O4, were clearly different from those on rOECs. Moreover, caOECs displayed their typical spindle-shaped morphology only upon growth factor/forskolin addition, whereas mitotically quiescent caOECs had a flattened morphology. Thus, caOECs can readily be purified from adult canine olfactory bulb and expanded by using established OEC mitogens. The behavior of caOECs toward forskolin suggests that caOECs and humOECs share a number of properties amd implies the presence of common intracellular signalling pathways. CaOECs therefore represent a suitable model system relevant for humOECs in neural repair studies.

Rapid Effects of Aldosterone

Not long ago, scientists celebrated the 50th birthday of aldosterone. And yet miracles around this dinosaur steroid hormone are creeping out of the bushes. For a long period, peaceful contentment overwhelmed even critical minds in the light of tremendous successes: the classical way of steroid action through a genomic machinery starting from the well-known intracellular receptors was close to being ideal in explaining both in vitro and in vivo data. The more recent findings on rapid effects of steroid hormones such as aldosterone including those of Fujita et al1 in this issue of Hypertension have stirred up our thinking about the mineralocorticoids and virtually all other steroid hormones. They cannot involve only genomic mechanisms because of their hasty appearance and, therefore, have been termed “nongenomic” effects. Such effects are all but new with the first report for a steroid hormone—progesterone—dating back to the 1940s,2 and those for aldosterone dating back to the 1950s and 1960s.3,4 However, as a consequence of vigorous efforts, the general scientific audience has gradually accepted their existence, and the mechanisms involved are being progressively investigated, at least up to a certain level. Over the past decade, it has become increasingly clear that those novel steroid actions use very common intracellular signaling pathways that are seemingly promiscuous and, thus, recruited by many other hormones that induce rapid signaling (eg, catecholamines). Though differing from steroid hormone to …

Presenilin-dependent Processing and Nuclear Function of γ-Protocadherins

The recently described protocadherin gene clusters encode cadherin-related proteins, which are highly expressed in the vertebrate nervous system. Here, we report biochemical studies addressing proteolytic processing of gamma-protocadherins. These type-I transmembrane proteins are cleaved by a metalloproteinase in vivo, generating a soluble extracellular fragment and a carboxyl-terminal fragment associated with the cellular membrane. In addition, we show that the carboxyl-terminal fragment is a substrate for further cleavage mediated by presenilin. Consequently, accumulation of the fragment is found when gamma-secretase is inactivated either by the specific presenilin-inhibitor L685,458 or in double mutant murine embryonic fibroblasts lacking both presenilin genes. The gamma-secretase-generated carboxyl-terminal fragment is largely unstable but accumulates when proteasomal degradation is inhibited. Interestingly, the proteolytic fragment generated by gamma-secretase can localize to the nucleus. This is the first report providing experimental evidence for a cell surface receptor signaling function of protocadherins regulated by proteolytic events.