A dynamic charge-charge interaction modulates PP2A:B56 substrate recruitment.

Xinru Wang,Wolfgang Peti,Isha Nasa,Jakob Nilsson,Dimitriya H Garvanska,Yumi Ueki,Rebecca Page,Arminja N Kettenbach,Gang Zhang

doi:10.7554/elife.55966

Abstract

The recruitment of substrates by the ser/thr protein phosphatase 2A (PP2A) is poorly understood, limiting our understanding of PP2A-regulated signaling. Recently, the first PP2A:B56 consensus binding motif, LxxIxE, was identified. However, most validated LxxIxE motifs bind PP2A:B56 with micromolar affinities, suggesting that additional motifs exist to enhance PP2A:B56 binding. Here, we report the requirement of a positively charged motif in a subset of PP2A:B56 interactors, including KIF4A, to facilitate B56 binding via dynamic, electrostatic interactions. Using molecular and cellular experiments, we show that a conserved, negatively charged groove on B56 mediates dynamic binding. We also discovered that this positively charged motif, in addition to facilitating KIF4A dephosphorylation, is essential for condensin I binding, a function distinct and exclusive from PP2A-B56 binding. Together, these results reveal how dynamic, charge-charge interactions fine-tune the interactions mediated by specific motifs, providing a new framework for understanding how PP2A regulation drives cellular signaling.

Highlights

Protein serine/threonine phosphatase 2A (PP2A) is one of the defining members of the ser/thr phosphoprotein phosphatase (PPP) family that, together with protein phosphatase 1 (PP1), regulates over 90% of all ser/thr dephosphorylation events in eukaryotic cells (Eichhorn et al, 2009)
PP2A is recognized as a tumor suppressor because its inactivation by small molecules, viral proteins or endogenous inhibitors leads to tumor formation (Bialojan and Takai, 1988; Pallas et al, 1990; Ruvolo, 2016; Williams et al, 2019)
A subset of PP2A:B56 specific substrates depend on a conserved acidic patch in B56 for PP2A:B56 binding

Summary

Introduction

Protein serine/threonine phosphatase 2A (PP2A) is one of the defining members of the ser/thr phosphoprotein phosphatase (PPP) family that, together with protein phosphatase 1 (PP1), regulates over 90% of all ser/thr dephosphorylation events in eukaryotic cells (Eichhorn et al, 2009). Cellular and biochemical studies further confirmed this by demonstrating the role of PP2A in orchestrating mitotic events, cell apoptosis, metabolism and many other fundamental cellular signaling pathways (Nilsson, 2019; Reid et al, 2013; Reynhout and Janssens, 2019; Wlodarchak and Xing, 2016). The A and C subunits form the PP2A core enzyme. This core enzyme is relatively invariant, the variable and interchangeable regulatory B subunits result in a diversity of distinct PP2A holoenzymes. There are four known families of B subunits, B55 (B’), B56 (B’, PR61), PR72 (B’’), and PR93 (B’’’), that differ in both their primary sequences and tertiary

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