Transcriptional activator TAp63 is upregulated in muscular atrophy during ALS and induces the pro-atrophic ubiquitin ligase Trim63.

Mechanisms of muscle atrophy are complex and their understanding might help finding therapeutic solutions for pathologies such as amyotrophic lateral sclerosis (ALS). We meta-analyzed transcriptomic experiments of muscles of ALS patients and mouse models, uncovering a p53 deregulation as common denominator. We then characterized the induction of several p53 family members (p53, p63, p73) and a correlation between the levels of p53 family target genes and the severity of muscle atrophy in ALS patients and mice. In particular, we observed increased p63 protein levels in the fibers of atrophic muscles via denervation-dependent and -independent mechanisms. At a functional level, we demonstrated that TAp63 and p53 transactivate the promoter and increased the expression of Trim63 (MuRF1), an effector of muscle atrophy. Altogether, these results suggest a novel function for p63 as a contributor to muscular atrophic processes via the regulation of multiple genes, including the muscle atrophy gene Trim63.

Role of Ca2+ in the secretory and biosynthetic response of porcine gonadotropes to substance P and gonadotropin-releasing hormone.

Substance P has been previously shown to stimulate luteinizing hormone (LH) secretion and synergistically enhance gonadotropin-releasing hormone (GnRH)-evoked LH release from cultured pig pituitary cells. To investigate the mechanisms involved in these responses, the effects of substance P (100 nM; 4 h) and/or GnRH (10 nM, 4 h) on LH release, LH intracellular content, and betaLH mRNA accumulation were evaluated in the absence or presence of extracellular Ca(2+). Likewise, the effects of substance P on the dynamics of cytosolic free Ca(2+) concentration ([Ca(2+)](i)) were examined in single cells. Extracellular Ca(2+) deprivation abolished both substance P- and GnRH-stimulated LH release, as well as their synergistic interaction. The substance P antagonist D-Arg1,D-Phe5,-Trp7,9,Leu11-substance P (100 nM) blocked the stimulatory effect of substance P on LH release and its interaction with GnRH without affecting GnRH-induced LH secretion. Whereas substance P did not modify betaLH transcript levels, GnRH stimulated betaLH mRNA accumulation through a mechanism dependent upon extracellular Ca(2+). Substance P directly increased [Ca(2+)](i) in a 30% of gonadotropes by causing two distinct types of response kinetics with single-peak (predominant, 83.3%) or sustained-plateau profiles. Reduction of external [Ca(2+)] decreased by half the percent of responsive cells, which only showed single-peak profiles. Taken together, our results demonstrate that the ability of substance P to stimulate basal and GnRH-induced LH release is exerted directly upon gonadotropes, is extracellular Ca(2+)-dependent and does not seem to require net increases in betaLH mRNA levels. Moreover, [Ca(2+)](i) measurements revealed that although substance P action in pig gonadotropes is strongly dependent on extracellular Ca(2+) influx, it would also involve intracellular Ca(2+) mobilization. Finally, extracellular Ca(2+) also plays a requisite role to sustain GnRH-stimulated increases in both betaLH mRNA and LH release.