A Calcineurin-dependent Switch Controls the Trafficking Function of α-Arrestin Aly1/Art6

Abstract

Background:In response to nutrient signals, ␣-arrestins selectively regulate trafficking of membrane transporters. Results: Aly1 is a substrate of the phosphatase calcineurin, and dephosphorylation triggers Aly1-dependent internalization of the permease Dip5. Conclusion: Endocytic function of ␣-arrestins is stimulated by removal of inhibitory phosphorylation. Significance: These insights define a molecular mechanism controlling the function of an ␣-arrestin in endocytosis, which is critical for cellular adaptation.

Specific α-Arrestins Negatively Regulate Saccharomyces cerevisiae Pheromone Response by Down-Modulating the G-Protein-Coupled Receptor Ste2

“…Assessment of Rsp5 copurification with ␣-arrestins was performed as described previously (78). To assess the state of ␣-arrestin modification by ubiquitin in vivo, BJ5459 GEV cells carrying a plasmid vector (pEGKG) for the expression of GST-Ldb19 or GST-Ldb19(K486R) were grown to midexponential phase and induced with 20 M ␤-estradiol (final concentration) for 3 h. After harvesting by centrifugation, the cells were washed and frozen in liquid N 2 .…”

“…Second, we showed previously that optimal CN function is required for efficient adaptation after MATa cells are exposed to ␣-factor (115). Third, we demonstrated recently that CN-mediated dephosphorylation of another ␣-arrestin, Aly1, is required to promote endocytosis of the aspartate and glutamate transporter Dip5 (78). Finally, like Aly1, Rod1 was identified in a global screen for CN substrates and found to be efficiently dephosphorylated by CN in vitro (116).…”

“…First, Snf1 cannot be the only protein kinase responsible for phosphorylating and inhibiting Rod1. In fact, phosphorylation seems to be a general mechanism for blocking the endocytic action of other ␣-arrestin family members (78,108,139). Second, it is clear, at least in the case of Rod1, that the same ␣-arrestin is being subjected to differential phospho-regulation as a means to control endocytosis of different targets in response to distinct stimuli.…”

“…It has been demonstrated that the cognate ␣-arrestin itself becomes ubiquitinylated during the process of recruiting Rsp5 to nutrient permeases (57,58,78,102,108). Moreover, the Lys residues in Ldb19 and Rod1 that are ubiquiti- (Fig.…”

Regulation of the Yeast Hxt6 Hexose Transporter by the Rod1 α-Arrestin, the Snf1 Protein Kinase, and the Bmh2 14-3-3 Protein

“…In this case, the Sit4 phosphatase has been proposed to be involved in Bul1 and Bul2 dephosphorylation, leading to their activation and subsequent down-regulation of Gap1 under the appropriate conditions, although direct dephosphorylation of Bul1 and Bul2 by Sit4 was not demonstrated. In addition, the calcineurin phosphatase was shown to directly dephosphorylate another Rsp5 adaptor Aly2, promoting its endocytic activity for Dip5, but not for Gap1 (14). These studies show that complex regulatory routes are employed to fine-tune the cohort of transport proteins present in the plasma membrane in response to the quality of the nitrogen source.…”