Activated CRH receptors inhibit autophagy by repressing conversion of LC3BI to LC3BII

Clinical studies have elucidated the negative correlation between microtubules-associated protein 1 light chain 3-B (LC3B) protein expression and overall survival of breast cancer patients. Our previous data demonstrated corticortropin-releasing hormone family (CRHs) suppressed migration of breast cancer cells via CRH receptors (CRHRs). Here, we showed that the activation of CRHRs (CRHR1 and CRHR2) remarkably reduced the conversion of LC3BI to LC3BII and hence repressed macroautophagy/autophagy, resulting in migration inhibition. By means of RT-4 cells (expressing higher CRHR1) with stable CRHR1 silence which was constructed by lentivirus with short hairpin RNA, we further confirmed CRH-inhibited LC3BII conversion. Using CRHRs agonists and antagonists, we found CRHRs triggered a marked reduction in the number of LC3B dots in both RT-4 and Hela cells(expressing higher CRHR2) which stably express RFP-GFP-LC3B. Of note, this decreased amount of autophagosome was associated with activation of Phospholipase C beta (PLC beta)-Inositol triphosphate (IP3)-mTOR signaling. Earle's Balanced Salt Solution (EBSS) decreased the expression of the key focal adhesion protein, paxillin, which was recovered by CRHRs ligands (CRH and UCN2). The effect of CRHRs ligands on paxillin resulted in the suppression of cell migration. Altogether, these data reveal a new link between CRHRs signaling and autophagy, and may help to envisage therapeutic strategies in cancer cell invasion.