The phosphatase Glc7 controls eisosomal response to starvation via posttranslational modification of Pil1

Abstract

ABSTRACTThe yeast plasma membrane (PM) is organised into specific subdomains that can regulate the activity of surface membrane proteins localised within them. Nutrient transporters actively uptake substrates in particular regions of the PM where they are also susceptible to the endocytic machinery for substrate induced degradation. However, transporters also diffuse into distinct subdomains termed eisosomes, where they are inactive for substrate uptake and are protected from endocytosis. Although most nutrient transporter populations are sorted to the vacuole for degradation during glucose starvation, a small pool are retained in eisosomes. Sequestering this small pool of transporters during nutrient stress is essential for efficient recovery from starvation following a return to replete conditions. However, the mechanisms controlling this process at a biochemical level are poorly defined. We find the core eisosome subunit Pil1, a Bin, Amphiphysin and Rvs. (BAR) domain protein involved in membrane dynamics required for eisosome biogenesis, is primarily phosphorylated by Pkh2 but that Pil1 dephosphorylation occurs during acute glucose starvation. We screened for enzyme localisation and activity to implicate the essential phosphatase Glc7 as the primary enzyme responsible for Pil1 dephosphorylation. Manipulation of GLC7 expression correlates with Pil1 hypo/hyper phosphorylation. Furthermore, glc7 mutants and Pil1-phosphomutants are defective in recovering from glucose starvation. We propose precise posttranslational control of Pil1 modulates nutrient transporter retention within eisosomes depending on cellular nutritional status, to maximise recovery from starvation.