Ca(2+)-mediated mitochondrial ROS metabolism augments Wnt/β-catenin pathway activation to facilitate cell differentiation

Emerging evidence suggests that reactive oxygen species (ROS) can stimulate Wnt/{beta}-catenin pathway in a number of cellular processes. However, potential sources of endogenous ROS have not been thoroughly explored. Here, we show that growth factor depletion in human neural progenitor cells induces ROS production in mitochondria. Elevated ROS levels augment activation of Wnt/{beta}-catenin signaling that regulates neural differentiation. We find that growth factor depletion stimulates release of Ca(2+) from the endoplasmic reticulum stores that subsequently accumulates in the mitochondria and triggers ROS production. The inhibition of mitochondrial Ca(2+) uptake with simultaneous growth factor depletion prevents the rise in ROS metabolism. Moreover, low ROS levels block the dissociation of the Wnt effector Dishevelled from Nucleoredoxin. Attenuation of the response amplitudes of pathway effectors delays the onset of Wnt/{beta}-catenin pathway activation and results in markedly impaired neuronal differentiation. Our findings reveal Ca(2+)-mediated ROS metabolic cues that finetune the efficiency of cell differentiation by modulating the extent of the Wnt/{beta}-catenin signaling output

Wnt11/Fzd7 signaling compartmentalizes AKAP2/PKA to regulate L-type Ca2+ channel

Calcium influx through the voltage-gated L-type calcium channels (LTCC) mediates a wide range of physiological processes from contraction to secretion. Despite extensive research on regulation of LTCC conductance by PKA phosphorylation in response to β-adrenergic stimulation, the science remains incomplete. Here, we show that Wnt11, a non-canonical Wnt ligand, through its G protein-coupled receptor (GPCR) Fzd7 attenuates the LTCC conductance by preventing the proteolytic processing of its C terminus. This is mediated across species by protein kinase A (PKA), which is compartmentalized by A-kinase anchoring proteins (AKAP). Systematic analysis of all AKAP family members revealed AKAP2 anchoring of PKA is central to the Wnt11-dependent regulation of the channel. The identified Wnt11/AKAP2/PKA signalosome is required for heart development, controlling the intercellular electrical coupling in the developing zebrafish heart. Altogether, our data revealed Wnt11/Fzd7 signaling via AKAP2/PKA as a conserved alternative GPCR system regulating Ca(2+) homeostasis

The Mitochondrial Ca(2+) Uniporter: Structure, Function, and Pharmacology.

Mitochondrial Ca(2+) uptake is crucial for an array of cellular functions while an imbalance can elicit cell death. In this chapter, we briefly reviewed the various modes of mitochondrial Ca(2+) uptake and our current understanding of mitochondrial Ca(2+) homeostasis in regards to cell physiology and pathophysiology. Further, this chapter focuses on the molecular identities, intracellular regulators as well as the pharmacology of mitochondrial Ca(2+) uniporter complex

Neuronal development is promoted by weakened intrinsic antioxidant defences due to epigenetic repression of Nrf2

Forebrain neurons have weak intrinsic antioxidant defences compared with astrocytes, but the molecular basis and purpose of this is poorly understood. We show that early in mouse cortical neuronal development in vitro and in vivo, expression of the master-regulator of antioxidant genes, transcription factor NF-E2-related-factor-2 (Nrf2), is repressed by epigenetic inactivation of its promoter. Consequently, in contrast to astrocytes or young neurons, maturing neurons possess negligible Nrf2-dependent antioxidant defences, and exhibit no transcriptional responses to Nrf2 activators, or to ablation of Nrf2’s inhibitor Keap1. Neuronal Nrf2 inactivation seems to be required for proper development: in maturing neurons, ectopic Nrf2 expression inhibits neurite outgrowth and aborization, and electrophysiological maturation, including synaptogenesis. These defects arise because Nrf2 activity buffers neuronal redox status, inhibiting maturation processes dependent on redox-sensitive JNK and Wnt pathways. Thus, developmental epigenetic Nrf2 repression weakens neuronal antioxidant defences but is necessary to create an environment that supports neuronal development

Nuclear translocation of the cardiac L-type calcium channel C-terminus is regulated by sex and 17β-estradiol

The cardiac voltage gated l-type Ca2+ channel (Cav1.2) constitutes the main entrance gate for Ca2+ that triggers cardiac contraction. Several studies showed that the distal C-terminus fragment of Cav1.2 alpha1C subunit (alpha1C-dCT) is proteolytically cleaved and shuttles between the plasma membrane and the nucleus, which is regulated both developmentally and by Ca2+. However, the effects of sex and sex hormone 17beta-estradiol (E2, estrogen) on alpha1C-dCT nuclear translocation are still unexplored. To investigate the sexual disparity in the alpha1C-dCT nuclear translocation, we first generated an antibody directed against a synthetic peptide (GRRASFHLE) located in alpha1C-dCT, and used it to probe ventricular myocytes from adult female and male mice. Immunocytochemistry of isolated mouse primary adult ventricular myocytes revealed both nuclear staining and cytosolic punctuate staining around the T-tubules. The ratio of nuclear to cytosolic intensity (Inuc/Icyt) was significantly higher in isolated female cardiomyocytes (1.42+/-0.05) compared to male cardiomyocytes (1.05+/-0.02). Western blot analysis of nuclear fraction confirmed these data. Furthermore, we found a significant decrease in nuclear staining intensity of alpha1C-dCT in both female and male cardiomyocytes upon serum withdrawal for 18h (Inuc/Icyt 1.05+/-0.02 and 0.89+/-0.02, respectively). Interestingly, subsequent E2 treatment (10-8M) for 8h normalized the intracellular distribution of alpha1C-dCT in male cardiomyocytes (Inuc/Icyt 1.04+/-0.02), but not in female cardiomyocytes. Acute treatment of male cardiomyocytes with E2 for 45min revealed a similar effect. This effect of E2 was revised by ICI indicating the involvement of ER in this signaling pathway. Taken together, our results showed that the shuttling of alpha1C-CT in cardiomyocytes is regulated in a sex-dependent manner, and E2-activated ER may play a role in the nuclear shuttling of alpha1C-dCT in male cardiomyocytes. This may explain, at least partly, the observed sex differences in the regulation of cardiac Cav1.2 channel activity