Regulation of cell quiescence-proliferation balance by Ca2+-CaMKK-Akt signaling

Porcine transient receptor potential channel 1 promotes adipogenesis and lipid deposition

Adipose tissue, an important organ involved in energy metabolism and endocrine, is closely related to animal meat quality and human health. Transient receptor potential channel 1 (TRPC1), an ion transporter, is adipocytes' major Ca2+ entry channel. However, its function in fat deposition is poorly understood, particularly in pigs, which are both an ideal model for human obesity research and a primary meat source for human diets. In the present investigation, our findings demonstrate a prominent expression of TRPC1 within the adipose tissue of pigs with a strong fat deposition ability. Functional analysis showed that TRPC1 promotes primary preadipocyte proliferation and adipogenic differentiation. In vivo, transgenic mice expressing porcine TRPC1 exhibited aggravated high-fat diet-induced obesity, hepatic steatosis, and insulin resistance. Moreover, TRPC1 may facilitate adipogenesis via activating phosphatidylinositol 3 kinase/AKT and β-catenin signaling pathways. Our research underscores the pivotal role of porcine TRPC1 as a positive regulator in adipogenesis and lipid accumulation processes, providing a potential target for improving animal meat quality and treating obesity-related diseases in humans.

Overexpression of TRPV6 Inhibits Coronary Atherosclerosis-Related Inflammatory Response and Cell Apoptosis via the PKA/UCP2 Pathway

Objective: This research is aimed at unravelling the intricate relationship between transient receptor potential vanilloid 6 (TRPV6), protein kinase A (PKA), uncoupling protein 2 (UCP2), and atherosclerosis. By shedding light on the role of the TRPV6/PKA/UCP2 pathway in inhibiting inflammatory response and cell apoptosis in coronary atherosclerotic plaques, this study provides valuable insights into potential therapeutic targets for treating coronary artery disease (CAD). Methods: We established animal and cell models of atherosclerosis. The expression of TRPV6 was measured using immunohistochemistry and immunofluorescence. Cytokine levels were detected by enzyme-linked immunosorbent assay (ELISA). Cell viability and apoptosis ratio were measured using cell counting kit-8 (CCK-8) and flow cytometry. The binding relationship between TRPV6 and PKA was validated using chromatin immunoprecipitation (CHIP) and coimmunoprecipitation (CoIP). Finally, the expression of the TRPV6/PKA/UCP2 signaling pathway and apoptosis-related factors was detected using western blot (WB) and quantitative real-time polymerase chain reaction (qRT-PCR). Results: TRPV6 was significantly decreased in atherosclerosis mouse and cell model. CHIP and CoIP assays indicated that TRPV6 binds to PKA and positively regulated its expression in oxidized low-density lipoprotein (ox-LDL)-treated human umbilical vein endothelial cells (HUVECs). Overexpression of TRPV6 significantly increased cell viability and inhibited apoptosis, whereas silencing TRPV6 had the opposite effect. Additionally, the overexpression of TRPV6 remarkably declined the expression of tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-1 beta (IL-1β). However, after silencing PKA, this effect was partially reversed, the cell viability and inflammatory response remarkably enhanced, and apoptosis significantly declined in oe-TRPV6 + si-PKA group. Conclusions: In summary, our study demonstrated that TRPV6 inhibited apoptosis and inflammatory response in the atherosclerosis cell model through the regulation of the PKA/UCP2 pathway.

Environmental and molecular control of tissue-specific ionocyte differentiation in zebrafish

Organisms cope with environmental fluctuations and maintain fitness in part via reversible phenotypic changes (acclimation). Aquatic animals are subject to dramatic seasonal fluctuations in water salinity, which affect osmolarity of their cells and consequently cellular function. Mechanosensory lateral line hair cells detect water motion for swimming behavior and are especially susceptible to salinity changes due to their direct contact with the environment. To maintain hair cell function when salinity decreases, neuromast (Nm)-associated ionocytes differentiate and invade lateral line neuromasts. The signals that trigger the adaptive differentiation of Nm ionocytes are unknown. We demonstrate that new Nm ionocytes are rapidly specified and selectively triggered to proliferate by low Ca2+ and Na+/Cl- levels. We further show that Nm ionocyte recruitment and induction is affected by hair cell activity. Once specified, Nm ionocyte differentiation and survival are associated with sequential activation of different Notch pathway components, a process different from other tissue-specific ionocytes. In summary, we show how environmental changes activate a signaling cascade that leads to physiological adaptation. This may prove essential for survival not only in seasonal changing environments but also in changing climates.

The involvement of CaMKKI in activating AMPKα in yesso scallop Patinopecten yessoensis under high temperature stress

Calcium/calmodulin dependent protein kinase kinase (CaMKK), a highly conserved protein kinase, is involved in the downstream processes of various biological activities by phosphorylating and activating 5'-AMP-activated protein kinase (AMPK) in response to the increase of cytosolic-free calcium (Ca2+). In the present study, a CaMKKI was identified from Yesso scallop Patinopecten yessoensis. Its mRNA was ubiquitously expressed in haemocytes and all tested tissues with the highest expression level in mantle. The expression level of PyCaMKKI mRNA in adductor muscle was significantly upregulated at 1, 3 and 6 h after high temperature treatment (25 °C), which was 3.43-fold (p < 0.05), 5.25-fold (p < 0.05), and 5.70-fold (p < 0.05) of that in blank group, respectively. At 3 h after high temperature treatment (25 °C), the protein level of PyAMPKα, as well as the phosphorylation level of PyAMPKα at Thr170 in adductor muscle, and the positive co-localized fluorescence signals of PyCaMKKI and PyAMPKα in haemocyte all increased significantly (p < 0.05) compared to blank group (18 °C). The pull-down assay showed that rPyCaMKKI and rPyAMPKα could bind each other in vitro. After PyCaMKKI was silenced by siRNA, the mRNA and protein levels of PyCaMKKI and PyAMPKα, and the phosphorylation level of PyAMPKα at Thr170 in adductor muscle were significantly down-regulated (p < 0.05) compared with the negative control group receiving an injection of siRNA-NC. These results collectively suggested that PyCaMKKI was involved in the activation of PyAMPKα in response to high temperature stress and would be helpful for understanding the function of PyCaMKKI-PyAMPKα pathway in maintaining energy homeostasis under high temperature stress in scallops.

Environmental and molecular control of tissue-specific ionocyte differentiation in zebrafish

Organisms adjust their physiology to cope with environmental fluctuations and maintain fitness. These adaptations occur via genetic changes over multiple generations or through acclimation, a set of reversible phenotypic changes that confer resilience to the individual. Aquatic organisms are subject to dramatic seasonal fluctuations in water salinity, which can affect the function of lateral line mechanosensory hair cells. To maintain hair cell function when salinity decreases, ion-regulating cells, Neuromast-associated ionocytes (Nm ionocytes), increase in number and invade lateral line neuromasts. How environmental changes trigger this adaptive differentiation of Nm ionocytes and how these cells are specified is still unknown. Here, we identify Nm ionocyte progenitors as foxi3a/foxi3b-expressing skin cells and show that their differentiation is associated with sequential activation of different Notch pathway components, which control ionocyte survival. We demonstrate that new Nm ionocytes are rapidly specified by absolute salinity levels, independently of stress response pathways. We further show that Nm ionocyte differentiation is selectively triggered by depletion of specific ions, such as Ca2+ and Na+/Cl-, but not by low K+ levels, and is independent of media osmolarity. Finally, we demonstrate that hair cell activity plays a role in Nm ionocyte recruitment and that systemic factors are not necessary for Nm ionocyte induction. In summary, we have identified how environmental changes activate a signaling cascade that triggers basal skin cell progenitors to differentiate into Nm ionocytes and invade lateral line organs. This adaptive behavior is an example of physiological plasticity that may prove essential for survival in changing climates.

Insulin signaling in development

Nutrient intake is obligatory for animal growth and development, but nutrients alone are not sufficient. Indeed, insulin and homologous hormones are required for normal growth even in the presence of nutrients. These hormones communicate nutrient status between organs, allowing animals to coordinate growth and metabolism with nutrient supply. Insulin and related hormones, such as insulin-like growth factors and insulin-like peptides, play important roles in development and metabolism, with defects in insulin production and signaling leading to hyperglycemia and diabetes. Here, we describe the insulin hormone family and the signal transduction pathways activated by these hormones. We highlight the roles of insulin signaling in coordinating maternal and fetal metabolism and growth during pregnancy, and we describe how secretion of insulin is regulated at different life stages. Additionally, we discuss the roles of insulin signaling in cell growth, stem cell proliferation and cell differentiation. We provide examples of the role of insulin in development across multiple model organisms: Caenorhabditis elegans, Drosophila, zebrafish, mouse and human.

Adhesion GPCR Gpr126 (Adgrg6) Expression Profiling in Zebrafish, Mouse, and Human Kidney

Adhesion G protein-coupled receptors (aGPCRs) comprise the second-largest class of GPCRs, the most common target for approved pharmacological therapies. aGPCRs play an important role in development and disease and have recently been associated with the kidney. Several aGPCRs are expressed in the kidney and some aGPCRs are either required for kidney development or their expression level is altered in diseased kidneys. Yet, general aGPCR function and their physiological role in the kidney are poorly understood. Here, we characterize in detail Gpr126 (Adgrg6) expression based on RNAscope® technology in zebrafish, mice, and humans during kidney development in adults. Gpr126 expression is enriched in the epithelial linage during nephrogenesis and persists in the adult kidney in parietal epithelial cells, collecting ducts, and urothelium. Single-cell RNAseq analysis shows that gpr126 expression is detected in zebrafish in a distinct ionocyte sub-population. It is co-detected selectively with slc9a3.2, slc4a4a, and trpv6, known to be involved in apical acid secretion, buffering blood or intracellular pH, and to maintain high cytoplasmic Ca2+ concentration, respectively. Furthermore, gpr126-expressing cells were enriched in the expression of potassium transporter kcnj1a.1 and gcm2, which regulate the expression of a calcium sensor receptor. Notably, the expression patterns of Trpv6, Kcnj1a.1, and Gpr126 in mouse kidneys are highly similar. Collectively, our approach permits a detailed insight into the spatio-temporal expression of Gpr126 and provides a basis to elucidate a possible role of Gpr126 in kidney physiology.

ROS signaling-induced mitochondrial Sgk1 expression regulates epithelial cell renewal

Many types of differentiated cells can reenter the cell cycle upon injury or stress. The underlying mechanisms are still poorly understood. Here, we investigated how quiescent cells are reactivated using a zebrafish model, in which a population of differentiated epithelial cells are reactivated under a physiological context. A robust and sustained increase in mitochondrial membrane potential was observed in the reactivated cells. Genetic and pharmacological perturbations show that elevated mitochondrial metabolism and ATP synthesis are critical for cell reactivation. Further analyses showed that elevated mitochondrial metabolism increases mitochondrial ROS levels, which induces Sgk1 expression in the mitochondria. Genetic deletion and inhibition of Sgk1 in zebrafish abolished epithelial cell reactivation. Similarly, ROS-dependent mitochondrial expression of SGK1 promotes S phase entry in human breast cancer cells. Mechanistically, SGK1 coordinates mitochondrial activity with ATP synthesis by phosphorylating F1Fo-ATP synthase. These findings suggest a conserved intramitochondrial signaling loop regulating epithelial cell renewal.

Nuciferine attenuates atherosclerosis by regulating the proliferation and migration of VSMCs through the Calm4/MMP12/AKT pathway in ApoE(-/-) mice fed with High-Fat-Diet

BACKGROUND

Atherosclerosis (AS) is the pathological basis of multiple cardiovascular diseases. The pathogenesis of AS is closely related to the abnormal proliferation and migration of vascular smooth muscle cells (VSMCs). Nuciferine, an aporphine alkaloid from lotus leaf, has various pharmacological activities. However, the effect and mechanism of nuciferine on regulating proliferation and migration of VSMCs against AS is still unclear.

PURPOSE

To elucidate the pharmacological effect and molecular mechanism of nuciferine on AS in ApoE^(-/-) mice fed with High-Fat-Diet (HFD).

STUDY DESIGN

HFD-fed ApoE^(-/-) mice and 3% fetal bovine serum (FBS) induced mouse aortic vascular smooth muscle cells (MOVAS) were used to investigate the protective effect and mechanism of nuciferine on AS.

METHODS

Oil red O staining was used to detect the atherosclerotic lesions. Western blotting and immunofluorescence were used to determine calmodulin 4 (Calm4) expression and localization. CCK-8 assay, transwell and wound-healing assays were used to measure the migration and proliferation of MOVAS cells.

RESULTS

Nuciferine at 40 mg/kg significantly ameliorated the aortic lesion and vascular plaque in AS model, which was equal to the effect of the positive control drug (atorvastatin). In addition, nuciferine attenuated the migration and proliferation of VSMCs in vivo and in vitro. Importantly, nuciferine down-regulated the increase of Calm4 induced by HFD-fed in ApoE^(-/-) mice or 3% FBS induced MOVAS cells. However, the inhibitory effect of nuciferine on the migration and proliferation of MOVAS cells was blocked when Calm4 was overexpressed. Furthermore, we found that nuciferine suppressed MMP12 and PI3K/Akt signaling pathway via Calm4.

CONCLUSION

Our results illustrated that Calm4 promoted the proliferation and motility of MOVAS by activating MMP12/Akt signaling pathway in AS. Nuciferine has a significant anti-atherogenic effect by regulating the proliferation and migration of VSMCs through the Calm4/MMP12/AKT signaling pathway. Thus, Calm4 could potentially be a new target for AS therapy, and nuciferine could be a potential drug against AS.

Molecular Mechanisms Underlying Ca2+/Calmodulin-Dependent Protein Kinase Kinase Signal Transduction

Ca²⁺/calmodulin-dependent protein kinase kinase (CaMKK) is the activating kinase for multiple downstream kinases, including CaM-kinase I (CaMKI), CaM-kinase IV (CaMKIV), protein kinase B (PKB/Akt), and 5′AMP-kinase (AMPK), through the phosphorylation of their activation-loop Thr residues in response to increasing the intracellular Ca²⁺ concentration, as CaMKK itself is a Ca²⁺/CaM-dependent enzyme. The CaMKK-mediated kinase cascade plays important roles in a number of Ca²⁺-dependent pathways, such as neuronal morphogenesis and plasticity, transcriptional activation, autophagy, and metabolic regulation, as well as in pathophysiological pathways, including cancer progression, metabolic syndrome, and mental disorders. This review focuses on the molecular mechanism underlying CaMKK-mediated signal transduction in normal and pathophysiological conditions. We summarize the current knowledge of the structural, functional, and physiological properties of the regulatory kinase, CaMKK, and the development and application of its pharmacological inhibitors.