Two cyclic AMP sources are critical for signaling of the GPCR CRHR1.

SILBERSTEIN, S.; INDA, C.; BONFIGLIO, J. J.; ARZT, E.; SENIN, S.; DOS SANTOS CLARO, P.

Bariloche

Congreso; The Third South American Symposium in Signal Transduction and Molecular Medicine? (SISTAM 2015); 2015

Corticotropin-releasing hormone (CRH) and its type 1 receptor (CRHR1) coordinate the neuroendocrine and behavioral adaptation to stress and are causally linked to affective disorders. In extra-hypothalamic circuits, CRH functions as a neuromodulator affecting neuronal architecture and synaptic transmission. We are exploring the CRHR1 signaling network to identify mechanisms involved in CRH action. In most systems, activated CRHR1 binds the Gs protein, resulting in transmembrane adenylyl cyclases (tmACs) activation and cAMP increase. For the first time, we describe that CRHR1 triggered cAMP response depends both on tmACs and on the atypical soluble adenylyl cyclase (sAC) in two relevant physiological cellular contexts of CRH action. Using FRET-based biosensors, specific pharmacological inhibitors and gene silencing, we demonstrated that both tmACs and sAC are involved in CRH-triggered cAMP response in the hippocampal neuronal HT22 cells. To assess whether tmACs and sAC act distinctly or contribute to a common pool of cAMP, we studied PKA and ERK1/2 responses as well as cell morphological changes. We found that CRH-induced sAC dependent cAMP is also required for ERK1/2 activation in mouse corticotrophs ATt20 cells. Endogenous sAC activity is not a general mediator of ERK1/2 activation in our model systems, since pharmacological inhibition or sAC silencing did not affect cAMP dependent ERK1/2 activation from other stimuli, as isoproterenol and PACAP38. Moreover, the differential regulation of ERK1/2 time course activation and a specific role of sAC in CRH-mediated morphological changes suggest that tmACs- or sAC-generared cAMP may have differential biological meanings. We have identified a novel sAC-mediated signaling pathway downstream CRH-activated CRHR1, which together with the tmACs contributes to the global cAMP response to CRH in neuronal and endocrine contexts. These findings are highly significant in terms of the emerging appreciation of cAMP microdomains, and suggest that the different regulation of tmACs and sAC may contribute to build ligand-induced specific physiological responses.