A novel non-canonical mechanism of regulation of MST3 (mammalian Sterile20-related kinase 3).
The canonical pathway of regulation of the GCK (germinal centre kinase) III subgroup member, MST3 (mammalian Sterile20-related kinase 3), involves a caspase-mediated cleavage between N-terminal catalytic and C-terminal regulatory domains with possible concurrent autophosphorylation of the activation loop MST3(Thr(178)), induction of serine/threonine protein kinase activity and nuclear localization. We identified an alternative 'non-canonical' pathway of MST3 activation (regulated primarily through dephosphorylation) which may also be applicable to other GCKIII (and GCKVI) subgroup members. In the basal state, inactive MST3 co-immunoprecipitated with the Golgi protein GOLGA2/gm130 (golgin A2/Golgi matrix protein 130). Activation of MST3 by calyculin A (a protein serine/threonine phosphatase 1/2A inhibitor) stimulated (auto)phosphorylation of MST3(Thr(178)) in the catalytic domain with essentially simultaneous cis-autophosphorylation of MST3(Thr(328)) in the regulatory domain, an event also requiring the MST3(341-376) sequence which acts as a putative docking domain. MST3(Thr(178)) phosphorylation increased MST3 kinase activity, but this activity was independent of MST3(Thr(328)) phosphorylation. Interestingly, MST3(Thr(328)) lies immediately C-terminal to a STRAD (Sterile20-related adaptor) pseudokinase-like site identified recently as being involved in binding of GCKIII/GCKVI members to MO25 scaffolding proteins. MST3(Thr(178)/Thr(328)) phosphorylation was concurrent with dissociation of MST3 from GOLGA2/gm130 and association of MST3 with MO25, and MST3(Thr(328)) phosphorylation was necessary for formation of the activated MST3-MO25 holocomplex.
School of Biological Sciences, University of Reading, Whiteknights Campus, UK.
Stephen J
SJ
Fuller
Liam J
LJ
McGuffin
Andrew K
AK
Marshall
Alejandro
A
Giraldo
Sampsa
S
Pikkarainen
Angela
A
Clerk
Peter H
PH
Sugden
D000595:Amino Acid Sequence; D000818:Animals; D020134:Catalytic Domain; D006801:Humans; D008322:Mammals; D008969:Molecular Sequence Data; D032342:Muscle Cells / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D010766:Phosphorylation; D054648:Protein Phosphatase 2 / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D013912:Threonine / Q000235:genetics; D000099317:Hippo Kinases
D009419:Nerve Tissue Proteins; D054648:Protein Phosphatase 2; D017346:Protein Serine-Threonine Kinases; D013912:Threonine; C109163:STK24 protein, human; D000099317:Hippo Kinases; C517189:PPP2CA protein, human