Threonine 74 of MOB1 is a putative key phosphorylation site by MST2 to form the scaffold to activate nuclear Dbf2-related kinase 1

Abstract

Mammalian nuclear Dbf2-related (NDR) kinases (LATS1 and 2, NDR1 and 2) play a role in cell proliferation, apoptosis and morphological changes. These kinases are regulated by mammalian sterile 20-like kinases (MSTs) and Mps one binder (MOB) 1. Okadaic acid (OA), which activates MST2, facilitates the complex formation of MOB1, MST2 and NDR1 in HEK293FT cells. The in vitro biochemical study demonstrates the phosphorylation of MOB1 by MST2. The phosphorylated MOB1 alone is capable to partially activate NDR1 in vitro, but MST2 is also required for the full activation. The knockdown of MOB1 or MST2 abolishes the OAinduced NDR1 activation in HEK293FT cells. Among MOB1 mutants, in which each serine or threonine residue is replaced with alanine, MOB1 T74A and T181A mutants fail to activate NDR1. Thr74, but not Thr181, is phosphorylated by MST2 in vitro, although MOB1 is also phosphorylated by MST2 at other site(s). The interaction of MOB1 T74A with NDR1 is barely enhanced by OA treatment. These findings indicate that the phosphorylation of MOB1 at Thr74 by MST2 is essential to make a complex of MOB1, MST2 and NDR1, and to fully activate NDR1.

Dysregulated YAP1/TAZ and TGF-β signaling mediate hepatocarcinogenesis in Mob1a/1b -deficient mice

“…No differences in phospho-MST1, total MST1, or total SAV1 were detected. We then stimulated imMob1DKOLP ± Tmx cells with okadaic acid (OA), which activates MST1/2 (40), and performed immunoblotting after adjusting lysates to equality of LATS1 protein. Whereas OA-stimulated imMob1DKOLP-Tmx cells showed vigorous LATS1 phosphorylation, OA-stimulated imMob1DKOLP+Tmx cells did not (Fig.…”

The Hippo pathway regulates stem cell proliferation, self-renewal, and differentiation

“…The activation of Mst1/2 leads to phosphorylation and activation of their direct substrates, Lats1/2 (Chan et al, 2005). Mob1, which forms a complex with Lats1/2 (Chow et al, 2010), is also phosphorylated and activated by Mst1/2, resulting in enhanced interaction between Lats1/2 and Mob1 (Hirabayashi et al, 2008;Praskova et al, 2008). Similar to that in Drosophila, MST1/2/Sav1 and Lats1/2/Mob1 form a physical and functional core of the Hippo pathway.…”

The Fat and Warts signaling pathways: new insights into their regulation,mechanism and conservation

“…2B, compare with Fig. 2A), including: phosphorylation of Lats (Wts), Mob (Mats) and WW45 (Sav) proteins by Mst (Hpo) kinases (Callus et al, 2006;Chan et al, 2005;Hirabayashi et al, 2008;Praskova et al, 2008); the association of WW45 with Mst and Lats (Callus et al, 2006;Lee et al, 2008); a requirement for WW45 for the phosphorylation of Lats (Lee et al, 2008); the association of Mob and Lats and the consequent promotion of Lats autophosphorylation (Praskova et al, 2008); and the phosphorylation of the Yki homologue Yes-associated protein (Yap) by Lats (Dong et al, 2007;Hao et al, 2008;Zhang et al, 2008a;Zhao et al, 2007). Studies of Mst in mammalian cells have identified autophosphorylation as being a crucial regulatory step for Hpo/Mst (Glantschnig et al, 2002;Lee and Yonehara, 2002), and have identified an association of Mst with Ras association domain family proteins (Praskova et al, 2004), which was subsequently also observed in Drosophila (Polesello et al, 2006).…”