Proteins required for vacuolar function are targets of lysine polyphosphorylation in yeast

Abstract

Polyphosphates (polyP) are long chains of inorganic phosphates that can be attached to lysine residues of target proteins as a non-enzymatic post-translational modification. This modification, termed polyphosphorylation, may be particularly prevalent in bacterial and fungal species that synthesize and store large quantities of polyP. In this study, we applied a proven screening strategy to evaluate the polyphosphorylation status of over 200 candidate targets in the budding yeast S. cerevisiae. We report 8 new polyphosphorylated proteins that interact genetically and physically with a previously identified network of targets implicated in ribosome biogenesis. The expanded target network includes vacuolar proteins Prb1 and Apl5, whose modification with polyP suggests a model for feedback regulation of polyP synthesis, while raising additional questions regarding the location of polyphosphorylation in vivo.. CC-BY 4.0 International license a certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under

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“…Of particular interest is the role of lysine polyphosphorylation in ribosome biosynthesis in yeast and humans (Bentley‐DeSousa et al ., 2018; Lorenzo‐Orts et al ., 2020; McCarthy et al ., 2020). In yeast c .…”

“…Of particular interest is the role of lysine polyphosphorylation in ribosome biosynthesis in yeast and humans (Bentley-DeSousa et al, 2018;Lorenzo-Orts et al, 2020;McCarthy et al, 2020). In yeast c. 7% of proteins have one or more PASK-like motifs (stretches of 20 amino acids with up to at least 15 glutamate, aspartate and serine residues and at least one lysine residue), and the 17 known polyphosphorylated proteins are preferentially localized to the nucleolus.…”

Vtc5 is localized to the vacuole membrane by the conserved AP-3 complex to regulate polyphosphate synthesis in budding yeast

“…Polyphosphorylation is the non-enzymatic addition of polyP chains onto lysine residues, principally within poly-acidic, serine, and lysine (PASK) rich clusters 27,45 . We previously reported that Apl5 is polyphosphorylated in its C-terminus PASK cluster (amino acids 897-932) 46 . Therefore, to test if polyphosphorylation impacts Apl5's role in localizing GFP-Vtc5 to the vacuole membrane, we first deleted the PASK cluster in its entirety.…”

“…We recently described the Apl5 subunit of AP-3 as a target of lysine polyphoshorylation 46 . However, our analysis of mutant Apl5 that cannot be polyphosphorylated suggests that this modification does not impact GFP-Vtc5 delivery to the vacuole or other AP-3 related phenotypes that we tested.…”

The promises of lysine polyphosphorylation as a regulatory modification in mammals are tempered by conceptual and technical challenges

“…Subsequent work by our group screened PASK‐containing proteins in budding yeast to identify 23 additional targets of lysine polyphosphorylation, including a conserved network of proteins involved in ribosome biogenesis. [ 22,23 ] This work suggests that polyphosphorylation may impact many processes, rather than simply being a quirk of Nsr1 and Top1 biology. We suggest that polyphosphorylation may be a global PTM, although testing this assertion will require further study.…”