Biology subjects

Veis, J.

Publications and source records attributed to Veis, J..

3 recordsLinked to original sources

bioRxiv2025

A functional map of phosphoprotein phosphatase regulation identifies an evolutionary conserved reductase for the catalytic metal ions

Serine/Threonine phosphoprotein phosphatases (PPPs, PP1-PP7) are conserved metalloenzymes and central to intracellular signaling in eukaryotes, but the details of their regulation is poorly understood. To address this, we performed genome-wide CRISPR knockout and focused base editor screens in PPP perturbed conditions to establish a high-resolution functional map of PPP regulation that pinpoints novel regulatory mechanisms. Through this, we identify the orphan reductase CYB5R4 as an evolutionarily conserved activator of PP4 and PP6, but not the closely related PP2A. Heme binding is essential for CYB5R4 function and mechanistically involves the reduction of the metal ions in the active site. Importantly, CYB5R4-mediated activation of PP4 is critical for cell viability when cells are treated with DNA damage-inducing agents known to cause oxidative stress. The discovery of a dedicated PPP reductase points to shared regulatory principles with protein tyrosine phosphatases, where specific enzymes dictate activity by regulating the active site redox state. In sum, our work provides a resource for understanding PPP function and the regulation of intracellular signaling.

cell biology↗

bioRxiv2024

PHLPP2 is a pseudophosphatase that lost activity in the metazoan ancestor

The phosphoinositide 3-kinase (PI3K) pathway is a major regulator of cell and organismal growth. Consequently, hyperactivation of PI3K and its downstream effector kinase, Akt, is observed in many human cancers. PH domain leucine-rich repeat-containing protein phosphatases (PHLPP), two paralogous members of the metal-dependent protein phosphatase family, have been reported as negative regulators of Akt signaling and, therefore, tumor suppressors. However, the stoichiometry and identity of the bound metal ion(s), mechanism of action, and enzymatic specificity of these proteins are not known. Seeking to fill these gaps in our understanding of PHLPP biology, we unexpectedly discovered that PHLPP2 has no catalytic activity against the regulatory phosphorylation sites of Akt, nor the generic substrate para -nitrophenylphosphate. Instead, we found that PHLPP2 is a pseudophosphatase with a single zinc ion bound in its catalytic center. Furthermore, we found that current cancer genomics data do not support the proposed role of PHLPP1 or PHLPP2 as tumor suppressors. Phylogenetic analyses revealed an ancestral phosphatase that arose more than 1 Mya, but that lost activity at the base of the metazoan lineage. In summary, our results provide a molecular explanation for the inconclusive results that have hampered research on PHLPP and argue for a new focus on non-catalytic roles of PHLPP1 and PHLPP2. Significance StatementPHLPP1 and PHLPP2 have previously been reported as protein phosphatases that specifically inactivate Akt, a pro-growth and survival kinase hyperactivated in many human cancers. Unexpectedly, we found that purified PHLPP2 has no detectable enzymatic activity in vitro, an observation which can be rationalized by its unusual active site, which has diverged significantly from that of canonical metal-dependent phosphatases. Furthermore, we show that cancer genomics do not support a role for either PHLPP1 or PHLPP2 in cancer. Our findings argue for the exploration of alternative hypotheses regarding the role of PHLPP in Akt signaling and cancer, with a focus on its non-catalytic functions.

biochemistry↗

bioRxiv2020

PP2A-Rts1 antagonizes Rck2-mediated hyperosmotic stress signaling in yeast

In Saccharomyces cerevisiae impairment of protein phosphatase PP2ARts1 leads to temperature and hyperosmotic stress sensitivity, yet the underlying mechanism and the scope of action of the phosphatase in the stress response remain elusive. Using quantitative mass spectrometry-based approaches we have identified a set of putative substrate proteins that show both, hyperosmotic stress- and PP2ARts1-dependent changes in their phosphorylation pattern. A comparative analysis with published MS-shotgun data revealed that the phosphorylation status of many of these sites is regulated by the MAPKAP kinase Rck2, suggesting a node of regulation. Detailed gel mobility shift assays and protein-protein interaction analysis strongly suggest that Rck2 activity is directly regulated by PP2ARts1 via a SLiM B56-family interaction motif, uncovering a previously unknown mechanism of how PP2A influences the response to hyperosmotic stress in Yeast.

cell biology↗