SOCE (store-operated Ca2+ entry) is mediated via specific plasma membrane channels in response to ER (endoplasmic reticulum) Ca2+ store depletion. It has been proposed that more than one channel element can contribute to SOCE. In this paper, Dermot Cooper and colleagues have used a functional approach to show that the previously established dependence of ACs (adenylate cyclases) on SOCE can also use this additional channel element, specifically demonstrating a role for TRPC1 (transient receptor potential canonical 1) as an integral component of SOCE, alongside STIM1 (stromal interaction molecule 1) and Orai1, in regulating Ca2+ fluxes within AC microdomains and influencing cAMP production.
The intracellular kinase MEKK2 (mitogen-activated protein kinase/extracellular-signal-regulated kinase kinase kinase 2) is an upstream regulator of JNK (c-Jun N-terminal kinase), but additional functions for MEKK2 have not been well defined. In this paper, Bruce Cuevas and colleagues show how MEKK2 associates with the scaffold protein paxillin in tumour cell focal adhesions, promoting paxillin ubiquitylation and redistribution to the cytoplasm. MEKK2 silencing prolongs paxillin retention in focal adhesions; furthermore, MEKK2 requires both kinase activity and physical association with paxillin to promote ubiquitylation.
Glycogen synthase kinase 3 (GSK3) is essential for normal development and function of the central nervous system. It is especially important for regulating neurotransmission, although the downstream substrates mediating this function are not yet clear. In this paper, Graham Neely, Adam Cole and colleagues report that the lipid kinase phosphatidylinositol 4-kinase II α (PI4KIIα) is a novel substrate of GSK3 that regulates trafficking and cell-surface expression of neurotransmitter receptors in neurons. Their studies implicate signalling between GSK3 and PI4KIIα as a novel regulator of vesicular trafficking and neurotransmission in the brain.
The endothelial cells (ECs) that line the vascular lumen are exposed to a wide variety of environmental stresses, such as hypoxia. Maladaptation to stress in ECs is a key event in the development of cardiovascular disease, and sirtuin 3 (SIRT3) is an NAD+-dependent protein deacetylase that modulates various proteins to control mitochondrial function and metabolism. In this paper, Danny Ling Wang and colleagues show how SIRT3 stabilizes the forkhead box class O transcription factor FOXO3 via deacetylation, which enhances the mitochondrial antioxidant defence system to increase the adaptive capacity of ECs during hypoxia. Their results provide a direction for ameliorating the development of cardiovascular diseases.