The Structure of an NDR/LATS Kinase–Mob Complex Reveals a Novel Kinase–Coactivator System and Substrate Docking Mechanism

Abstract

Eukaryotic cells commonly use protein kinases in signaling systems that relay information and control a wide range of processes. These enzymes have a fundamentally similar structure, but achieve functional diversity through variable regions that determine how the catalytic core is activated and recruited to phosphorylation targets. “Hippo” pathways are ancient protein kinase signaling systems that control cell proliferation and morphogenesis; the NDR/LATS family protein kinases, which associate with “Mob” coactivator proteins, are central but incompletely understood components of these pathways. Here we describe the crystal structure of budding yeast Cbk1–Mob2, to our knowledge the first of an NDR/LATS kinase–Mob complex. It shows a novel coactivator-organized activation region that may be unique to NDR/LATS kinases, in which a key regulatory motif apparently shifts from an inactive binding mode to an active one upon phosphorylation. We also provide a structural basis for a substrate docking mechanism previously unknown in AGC family kinases, and show that docking interaction provides robustness to Cbk1’s regulation of its two known in vivo substrates. Co-evolution of docking motifs and phosphorylation consensus sites strongly indicates that a protein is an in vivo regulatory target of this hippo pathway, and predicts a new group of high-confidence Cbk1 substrates that function at sites of cytokinesis and cell growth. Moreover, docking peptides arise in unstructured regions of proteins that are probably already kinase substrates, suggesting a broad sequential model for adaptive acquisition of kinase docking in rapidly evolving intrinsically disordered polypeptides.

Mechanisms of Hippo pathway regulation

“…Moreover, another recent study using the crystal structure of the budding yeast homologs of NDR and MOB, Cbk1 and Mob2, shows that Mob2 binding to Cbk1 not only promotes enzymatic activity of Cbk1 but also creates a docking motif for Cbk1 substrates (Gogl et al 2015). This docking is crucial for robustness and substrate selectivity of Cbk1, which is unique among AGC family kinases, indicating a role of MOB in not only kinase activation but also substrate specificity.…”

MOB Co-activators Associate with NDR/LATS Kinases to Function in DNA Damage Response Signaling and Hippo Pathways

“…Many kinds of MOB-NDR/LATS kinase complexes are central to hippo signalling pathways, and these enzymes have a primarily similar structure, with the variable regions achieving functional diversity, and the catalytic core performing kinase activities. Very recently, Eric L. Weiss solved the structure of Cbk1-MOB2 complex, which is the first structure of NDR/LATS kinase-MOB complex, showing the binding of MOB coactivator can allosterically regulate the conformation of NDR/LATS kinase, indicating an activation mechanism unique to NDR/LATS kinases [4]. Further efforts are still needed to show the clear mechanism of how MOB2 and NDR/LATS kinases function in DDR signalling and cell cycle checkpoint.…”

“…In these systems, MST/hippo kinases together with MOB coactivators activate AGC kinases NDR/LATS, controlling cell fate and tissue architecture. NDR/LATS kinase-MOB coactivator modules are in the core position of all known hippo pathways [3,4].…”

“…In these systems, MST/hippo kinases together with MOB coactivators activate AGC kinases NDR/LATS, controlling cell fate and tissue architecture. NDR/LATS kinase-MOB coactivator modules are in the core position of all known hippo pathways [3,4].DNA damage response (DDR) is activated by a cascade of protein kinases that regulate DNA repair in both transcriptional and posttranslational levels. DDR signaling will persist until DNA repair process is completed, during which time cell circle will arrest.…”

Complex Haploinsufficiency-Based Genetic Analysis of the NDR/Lats Kinase Cbk1 Provides Insight into Its Multiple Functions in Candida albicans

“…Specifically, Luca and Winey (1998) showed that double mutants of mps1-1 and mob2D, the binding partner of Cbk1, showed increased ploidy relative to each single mutant. Inspection of the protein sequence of Cbk1 revealed the presence of a consensus Mps1 phosphorylation site (E/D/N/Q at the 22 position relative to S or T; Gogl et al 2015) at S98 (EMS) and data from a recent phosphoproteomic study indicate that this position is phosphorylated in C. albicans (Willger et al 2015). In addition, C. albicans Mob2 contains five consensus Mps1 sites that are also phosphorylated (NLS 35 ; NLS 44 ; QDS 83 ; QSS 86 ; and QSS 93 ) according to this study (Dou et al 2011).…”