Protein Kinase C Regulates ASIC1a Protein Expression and Channel Function via NF-kB Signaling Pathway

Temperature-induced embryonic diapause in chickens is mediated by PKC-NF-κB-IRF1 signaling

BACKGROUND

Embryonic diapause (dormancy) is a state of temporary arrest of embryonic development that is triggered by unfavorable conditions and serves as an evolutionary strategy to ensure reproductive survival. Unlike maternally-controlled embryonic diapause in mammals, chicken embryonic diapause is critically dependent on the environmental temperature. However, the molecular control of diapause in avian species remains largely uncharacterized. In this study, we evaluated the dynamic transcriptomic and phosphoproteomic profiles of chicken embryos in pre-diapause, diapause, and reactivated states.

RESULTS

Our data demonstrated a characteristic gene expression pattern in effects on cell survival-associated and stress response signaling pathways. Unlike mammalian diapause, mTOR signaling is not responsible for chicken diapause. However, cold stress responsive genes, such as IRF1, were identified as key regulators of diapause. Further in vitro investigation showed that cold stress-induced transcription of IRF1 was dependent on the PKC-NF-κB signaling pathway, providing a mechanism for proliferation arrest during diapause. Consistently, in vivo overexpression of IRF1 in diapause embryos blocked reactivation after restoration of developmental temperatures.

CONCLUSIONS

We concluded that embryonic diapause in chicken is characterized by proliferation arrest, which is the same with other spices. However, chicken embryonic diapause is strictly correlated with the cold stress signal and mediated by PKC-NF-κB-IRF1 signaling, which distinguish chicken diapause from the mTOR based diapause in mammals.

Acid-sensing ion channel 1a activates IKCa/SKCa channels and contributes to endothelium-dependent dilation

Acid-sensing ion channel 1a (ASIC1a) belongs to a novel family of proton-gated cation channels that are permeable to both Na+ and Ca2+. ASIC1a is expressed in vascular smooth muscle and endothelial cells in a variety of vascular beds, yet little is known regarding the potential impact of ASIC1a to regulate local vascular reactivity. Our previous studies in rat mesenteric arteries suggest ASIC1a does not contribute to agonist-induced vasoconstriction but may mediate a vasodilatory response. The objective of the current study is to determine the role of ASIC1a in systemic vasodilatory responses by testing the hypothesis that the activation of endothelial ASIC1a mediates vasodilation of mesenteric resistance arteries through an endothelium-dependent hyperpolarization (EDH)-related pathway. The selective ASIC1a antagonist psalmotoxin 1 (PcTX1) largely attenuated the sustained vasodilatory response to acetylcholine (ACh) in isolated, pressurized mesenteric resistance arteries and ACh-mediated Ca2+ influx in freshly isolated mesenteric endothelial tubes. Similarly, basal tone was enhanced and ACh-induced vasodilation blunted in mesenteric arteries from Asic1a knockout mice. ASIC1a colocalizes with intermediate- and small-conductance Ca2+-activated K+ channels (IKCa and SKCa, respectively), and the IKCa/SKCa-sensitive component of the ACh-mediated vasodilation was blocked by ASIC1a inhibition. To determine the role of ASIC1a to activate IKCa/SKCa channels, we measured whole-cell K+ currents using the perforated-patch clamp technique in freshly isolated mesenteric endothelial cells. Inhibition of ASIC1a prevented ACh-induced activation of IKCa/SKCa channels. The ASIC1 agonist, α/β-MitTx, activated IKCa/SKCa channels and induced an IKCa/SKCa-dependent vasodilation. Together, the present study demonstrates that ASIC1a couples to IKCa/SKCa channels in mesenteric resistance arteries to mediate endothelium-dependent vasodilation.

Modulators of ASIC1a and its potential as a therapeutic target for age-related diseases

Age-related diseases have become more common with the advancing age of the worldwide population. Such diseases involve multiple organs, with tissue degeneration and cellular apoptosis. To date, there is a general lack of effective drugs for treatment of most age-related diseases and there is therefore an urgent need to identify novel drug targets for improved treatment. Acid-sensing ion channel 1a (ASIC1a) is a degenerin/epithelial sodium channel family member, which is activated in an acidic environment to regulate pathophysiological processes such as acidosis, inflammation, hypoxia, and ischemia. A large body of evidence suggests that ASIC1a plays an important role in the development of age-related diseases (e.g., stroke, rheumatoid arthritis, Huntington's disease, and Parkinson's disease.). Herein we present: 1) a review of ASIC1a channel properties, distribution, and physiological function; 2) a summary of the pharmacological properties of ASIC1a; 3) and a consideration of ASIC1a as a potential therapeutic target for treatment of age-related disease.

Nesfatin-1 exerts protective effects on acidosis-stimulated chondrocytes and rats with adjuvant-induced arthritis by inhibiting ASIC1a expression

Nesfatin-1, a newly identified energy-regulating peptide, has been reported to possess antioxidant, anti-inflammatory, and antiapoptotic properties; however, to date, its effect on rheumatoid arthritis (RA) has not been previously explored in detail. We previously showed that activation of acid-sensing ion channel 1a (ASIC1a) by acidosis plays an important role in RA pathogenesis. Therefore, in this study, we evaluated the effects of nesfatin-1 on acidosis-stimulated chondrocyte injury in vitro and in vivo and examined the involvement of ASIC1a and the mechanism underlying the effects of nesfatin-1 on RA. Acid-stimulated articular chondrocytes were used to examine one of the several possible mechanisms underlying RA pathogenesis in vitro. The mRNA expression profile of acid-induced chondrocytes treated or not treated with nesfatin-1 was investigated by RNA sequencing. The effects of nesfatin-1 on oxidative stress, inflammation, and apoptosis in acid-induced chondrocytes were measured. The mechanistic effect of nesfatin-1 on ASIC1a expression and intracellular Ca²⁺ in acid-stimulated chondrocytes was studied. Rats with adjuvant-induced arthritis (AA) were used for in vivo analysis of RA pathophysiology. Cartilage degradation and ASIC1a expression in chondrocytes were detected in rats with AA after intraarticular nesfatin-1 injection. The in vitro experiments showed that nesfatin-1 decreased acidosis-induced cytotoxicity and elevation of intracellular Ca²⁺ levels in chondrocytes. Moreover, it attenuated acid-induced oxidative stress, inflammation, and apoptosis in chondrocytes. Nesfatin-1 decreased ASIC1a protein levels in acid-stimulated chondrocytes via the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) and nuclear factor kappa-B (NF-κB) signaling pathways. In vivo analysis showed that nesfatin-1 ameliorated cartilage degradation and decreased ASIC1a expression in the chondrocytes of rats with AA. Collectively, nesfatin-1 suppressed acidosis-induced oxidative stress, inflammation, and apoptosis in acid-stimulated chondrocytes and alleviated arthritis symptoms in rats with AA, and its mechanism may be related to its ability to decrease ASIC1a protein levels via the MAPK/ERK and NF-κB pathways.

PKC regulation of ion channels: The involvement of PIP2

Ion channels are integral membrane proteins whose gating has been increasingly shown to depend on the presence of the low-abundance membrane phospholipid, phosphatidylinositol (4,5) bisphosphate. The expression and function of ion channels is tightly regulated via protein phosphorylation by specific kinases, including various PKC isoforms. Several channels have further been shown to be regulated by PKC through altered surface expression, probability of channel opening, shifts in voltage dependence of their activation, or changes in inactivation or desensitization. In this review, we survey the impact of phosphorylation of various ion channels by PKC isoforms and examine the dependence of phosphorylated ion channels on phosphatidylinositol (4,5) bisphosphate as a mechanistic endpoint to control channel gating.

Hydrogen Sulfide Upregulates Acid-sensing Ion Channels via the MAPK-Erk1/2 Signaling Pathway

Hydrogen sulfide (H₂S) emerged recently as a new gasotransmitter and was shown to exert cellular effects by interacting with proteins, among them many ion channels. Acid-sensing ion channels (ASICs) are neuronal voltage-insensitive Na⁺ channels activated by extracellular protons. ASICs are involved in many physiological and pathological processes, such as fear conditioning, pain sensation, and seizures. We characterize here the regulation of ASICs by H₂S. In transfected mammalian cells, the H₂S donor NaHS increased the acid-induced ASIC1a peak currents in a time- and concentration-dependent manner. Similarly, NaHS potentiated also the acid-induced currents of ASIC1b, ASIC2a, and ASIC3. An upregulation induced by the H₂S donors NaHS and GYY4137 was also observed with the endogenous ASIC currents of cultured hypothalamus neurons. In parallel with the effect on function, the total and plasma membrane expression of ASIC1a was increased by GYY4137, as determined in cultured cortical neurons. H₂S also enhanced the phosphorylation of the extracellular signal-regulated kinase (pErk1/2), which belongs to the family of mitogen-activated protein kinases (MAPKs). Pharmacological blockade of the MAPK signaling pathway prevented the GYY4137-induced increase of ASIC function and expression, indicating that this pathway is required for ASIC regulation by H₂S. Our study demonstrates that H₂S regulates ASIC expression and function, and identifies the involved signaling mechanism. Since H₂S shares several roles with ASICs, as for example facilitation of learning and memory, protection during seizure activity, and modulation of nociception, it may be possible that H₂S exerts some of these effects via a regulation of ASIC function.