The phosphatase Glc7 controls the eisosomal response to starvation via post-translational modification of Pil1

Abstract

The yeast plasma membrane (PM) is organised into specific subdomains that regulate surface membrane proteins. Surface transporters actively uptake nutrients in particular regions of the PM where they are also susceptible to substrate induced endocytosis. However, transporters also diffuse into distinct subdomains termed eisosomes, where they are protected from endocytosis. Although most nutrient transporter populations are downregulated in the vacuole following glucose starvation, a small pool is retained in eisosomes to provide efficient recovery from starvation. We find the core eisosome subunit Pil1, a Bin, Amphiphysin and Rvs (BAR) domain protein required for eisosome biogenesis, is phosphorylated primarily by the kinase Pkh2. In response to acute glucose starvation, Pil1 is rapidly dephosphorylated. Enzyme localisation and activity screens implicate the phosphatase Glc7 is the primary enzyme responsible for Pil1 dephosphorylation. Both depletion of GLC7 and phospho-ablative or phospho-mimetic mutations of Pil1 correlate with Pil1 phosphorylation status, failure to properly retain transporters in eisosomes, and results in defective starvation recovery. We propose precise posttranslational control of Pil1 modulates nutrient transporter retention within eisosomes depending on extracellular nutrient levels, to maximise recovery following starvation.

Phosphoregulation of the yeast Pma1 H+-ATPase autoinhibitory domain involves the Ptk1/2 kinases and the Glc7 PP1 phosphatase and is under TORC1 control

“…Reg1 does not seem to play an important role in this Glc7 function, since a lack of Reg1 does not impair S911-T912 dephosphorylation in Pma1. We therefore propose that under glucose starvation, Glc7 associates with one or several other regulatory subunits to actively catalyze Pma1 S911-T912 dephosphorylation (Fig 6B) and potentially that of other proteins as well, as recently illustrated [59]. Our attempts to identify such Glc7 subunits by testing 22 single mutants were not successful, possibly because several of the tested proteins function redundantly with Glc7 to dephosphorylate S911-T912 in Pma1.…”

High resolution live cell imaging to define ultrastructural and dynamic features of the halotolerant yeastDebaryomyces hansenii

“…Finally, although we were not able to visualise eisosome compartments using fluorescent methods, we were at least able to detect levels of the core eisosome factor Pil1. As Pil1 is post-translationally regulated in response to nutrient stress (Laidlaw et al, 2021;Paine et al, 2023), and eisosomes are generally associated with stress conditions (Athanasopoulos et al, 2019;Babst, 2019), it would be interesting to know whether eisosomes are involved in D. Hansenii salt tolerance. These are just some tractable inferences that can be made despite being unable to genetically modify and visualise trafficking pathways and biological processes.…”

The PP2A-like phosphatase Ppg1 mediates assembly of the Far complex to balance gluconeogenic outputs and enables adaptation to glucose depletion

“…The PP1 phosphatase dephosphorylates and inactivates the Snf1 kinase to enable glucose-mediated catabolite repression in glucose-replete conditions [36,37]. PP1 also dephosphorylates a component of eisosomes in glucose-depleted conditions to regulate nutrient transporter availability at the plasma membrane, enabling cells to recover from glucose starvation [38]. Upon glucose starvation, PP2A phosphatases dephosphorylate stress-responsive transcription factors to transcriptionally regulate enzymes that increase the synthesis of storage carbohydrates [34,[39][40][41].…”