The C-terminal region of the yeast monocarboxylate transporter Jen1 acts as a glucose signal–responding degron recognized by the α-arrestin Rod1

Abstract

In response to changes in nutrient conditions, cells rearrange the composition of plasma membrane (PM) transporters to optimize their metabolic flux. Not only transcriptional gene regulation, but also inactivation of specific transporters is important for fast rearrangement of the PM. In eukaryotic cells, endocytosis plays a role in transporter inactivation, which is triggered by ubiquitination of these transporters. The Nedd4 family E3 ubiquitin ligase is responsible for ubiquitination of the PM transporters and requires that a series of α-arrestin proteins are targeted to these transporters. The mechanism by which an α-arrestin recognizes its cognate transporters in response to environmental signals is of intense scientific interest. Excess substrates or signal transduction pathways are known to initiate recognition of transporters by α-arrestins. Here, we identified an endocytic-sorting signal in the monocarboxylate transporter Jen1 from yeast (), whose endocytic degradation depends on the Snf1-glucose signaling pathway. We found that the C-terminal 20-amino acid-long region of Jen1 contains an amino acid sequence required for association of Jen1 to the α-arrestin Rod1, as well as lysine residues important for glucose-induced Jen1 ubiquitination. Notably, fusion of this region to the methionine permease, Mup1, whose endocytosis is normally induced by excess methionine, was sufficient for Mup1 to undergo glucose-induced, Rod1-mediated endocytosis. Taken together, our results demonstrate that the Jen1 C-terminal region acts as a glucose-responding degron for α-arrestin-mediated endocytic degradation of Jen1.

Molecular Basis of Zinc-Dependent Endocytosis of Human ZIP4 Transceptor

“…Our observation is also consistent with the previous report that the K476A mutation in the L2 of mouse ZIP4 (equivalent to K463 in hZIP4) did not affect the ectodomain shedding, which is an endocytosis-dependent process ( Kambe and Andrews, 2009 ). The ubiquitination-independent endocytosis of a nutrient transporter is unusual because substrate-stimulated endocytosis of many other nutrient transporters depends on ubiquitination ( Eguez et al, 2004 ; Erpapazoglou et al, 2008 ; Felice et al, 2005 ; Fujita et al, 2018 ; Galan et al, 1996 ; Gitan and Eide, 2000 ; Graschopf et al, 2001 ; Liu et al, 2007 ; Soetens et al, 2001 ). As far as we know, the only exception is the human copper transporter hCTR1, which reportedly undergoes endocytosis without degradation or ubiquitination upon low micromolar copper exposure for a short period of time ( Clifford et al, 2016 ; Molloy and Kaplan, 2009 ).…”

Regulation of Amino Acid Transport in Saccharomyces cerevisiae

“…Moreover, they showed that lysine residues prone to ubiquitination are found mostly in the N-terminal tail of plasma membrane YATs (274,278,(301)(302)(303). A note should be made here about the high-affinity monocarboxylate transporter Jen1, where lysine residues in the cytosolic loop region affect glucose-induced polyubiquitination, while the N-terminal lysine residues have no effect (304). Thus, the tail or loop regions that mediate endocytosis may vary for different transporter families.…”

Yeast α-arrestin Art2 is the key regulator of ubiquitylation-dependent endocytosis of plasma membrane vitamin B1 transporters

“…For instance, the accumulation of arginine appears to stimulate target of rapamycin complex 1 (TORC1) kinase, which simultaneously inhibits Npr1 kinase and stimulates Sit4 phosphatase, resulting in the Art1-mediated ubiquitylation of Can1 [27,29]. However in some cases (e.g., Gap1 and Jen1), ubiquitylation-induced endocytosis is initiated via the activation of the α-arrestin in response to substrate accumulation, and no additional structural rearrangement appears to be required [27,29,30]. Alternatively, a recent study demonstrated that the activation of TORC1 could be linked to the activity of the proton pump plasma membrane ATPase 1 (Pma1) and H + uptake by H + -amino acids symporters [31].…”