Differential NDR/LATS Interactions with the Human MOB Family Reveal a Negative Role for Human MOB2 in the Regulation of Human NDR Kinases

Abstract

MOB proteins are integral components of signaling pathways controlling important cellular processes, such as mitotic exit, centrosome duplication, apoptosis, and cell proliferation in eukaryotes. The human MOB protein family consists of six distinct members (human MOB1A [hMOB1A], -1B, -2, -3A, -3B, and -3C), with hMOB1A/B the best studied due to their putative tumor-suppressive functions through the regulation of NDR/LATS kinases. The roles of the other MOB proteins are less well defined. Accordingly, we characterized all six human MOB proteins in the context of NDR/LATS binding and their abilities to activate NDR/LATS kinases. hMOB3A/B/C proteins neither bind nor activate any of the four human NDR/LATS kinases. We found that both hMOB2 and hMOB1A bound to the N-terminal region of NDR1. However, our data suggest that the binding modes differ significantly. Our work revealed that hMOB2 competes with hMOB1A for NDR binding. hMOB2, in contrast to hMOB1A/B, is bound to unphosphorylated NDR. Moreover, RNA interference (RNAi) depletion of hMOB2 resulted in increased NDR kinase activity. Consistent with these findings, hMOB2 overexpression interfered with the functional roles of NDR in death receptor signaling and centrosome overduplication. In summary, our data indicate that hMOB2 is a negative regulator of human NDR kinases in biochemical and biological settings.

Mechanisms of Hippo pathway regulation

“…Interestingly, the interaction between MOB proteins (the human genome encodes six MOBs: MOB1A/B, MOB2, and MOB3A/B/C) and the N-terminal regulatory domain of the kinases is a common feature of NDR family kinases, although LATS1/2 and NDR1/2 appear to use distinct subsets of MOB proteins. MOB1A/B associate with both LATS1/2 and NDR1/2, while MOB2 mediates an inhibitory interaction with NDR1/2 but not with LATS1/2 Bothos et al 2005;Hergovich et al 2005;Kohler et al 2010).…”

Downstream of human NDR kinases: Impacting on c-myc and p21 protein stability to control cell cycle progression

“…In both flies and mammals, MOB1 proteins regulate both the NDR and the LATS branch, 5,[15][16][17][18][19][20] whereas the MOB2 protein specifically regulates the NDR branch. 6,15 Interestingly, it has been shown that in mammals and potentially also in flies, the MOB2 protein functions as an inhibitor of NDR signaling. 6 Furthermore, in D. melanogaster, one Ste-20-like kinase, Hippo (Hpo), can regulate both NDR/ LATS kinase family members.…”

“…6,15 Interestingly, it has been shown that in mammals and potentially also in flies, the MOB2 protein functions as an inhibitor of NDR signaling. 6 Furthermore, in D. melanogaster, one Ste-20-like kinase, Hippo (Hpo), can regulate both NDR/ LATS kinase family members. 8 Similar findings have been reported for the Ste-20-like kinases (MST kinases) in mammals.…”

“…detect a significant increase in activation of NDR in M phase, it remains to be confirmed that this function for NDR1 indeed depends on NDR kinase activity. Given that the mitotic role of NDR1 was proposed to dependent on an NDR1-hMOB2 complex, 45 and that hMOB2 has been found to inhibit NDR kinase activity, 6 we might speculate that NDR1 in mitosis could function as an adaptor molecule independent of NDR kinase activity. Interestingly, our work on NDR kinase downstream signaling mechanisms indicates that NDR1/2 kinases can have kinase activity-independent functions 23 and therefore might serve as adaptor molecules in more than one biological setting.…”

“…1 Mammalian cells express four different NDR/LATS kinases: NDR1, NDR2, LATS1 and LATS2, which indicates an increasing complexity in NDR/LATS kinase signaling from yeast to man. 4 Given that the primary sequences of NDR/LATS kinases are remarkably conserved, it is not surprising that all NDR/LATS kinases exhibit four conserved regulatory features: (1) an N-terminal regulatory domain (NTR), a platform for protein-protein interactions, 5,6 (2) a stretch of basic amino acids within the kinase domain, which acts as an auto-inhibitory sequence (AIS), 5 (3) an activation segment in proximity of the AIS and (4) a C-terminal hydrophobic motif. 7 Using genetic and biochemical analysis, it has been shown that NDR kinases across species are activated by hydrophobic motif phosphorylation mediated by members of the Ste-20-like family of protein kinases.…”