Ndr protein kinase is regulated by phosphorylation on two conserved sequence motifs.
Ndr is a nuclear serine/threonine protein kinase that belongs to a subfamily of kinases implicated in the regulation of cell division and cell morphology. This subfamily includes the kinases LATS, Orb6, Cot-1, and Dbf2. We show here that Ndr is potently activated when intact cells are treated with okadaic acid, suggesting that Ndr is normally held in a state of low activity by protein phosphatase 2A. We mapped the regulatory phosphorylation sites of Ndr protein kinase and found that active Ndr is phosphorylated on Ser-281 and Thr-444. Mutation of either site to alanine strongly reduced both basal and okadaic acid-stimulated Ndr activity, while combined mutation abolished Ndr activity completely. Importantly, each of these sites (and also the surrounding sequences) are conserved in the kinase relatives of Ndr, suggesting a general mechanism of activation for kinases of this subfamily. Ser-281 and Thr-444 are also similar to the regulatory phosphorylation sites in several targets of the phosphoinositide-dependent protein kinase PDK1.(1) However, PDK1 does not appear to function as an upstream kinase for Ndr. Thus, Ndr and its close relatives may operate in a novel signaling pathway downstream of an as-yet-unidentified kinase with specificity similar to, but distinct from, PDK1.
Millward
T A
TA
Friedrich Miescher-Institut, Maulbeerstrasse 66, CH-4058 Basel, Switzerland.
Hess
D
D
Hemmings
B A
BA
D064413:3-Phosphoinositide-Dependent Protein Kinases; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002461:Cell Line, Transformed; D017124:Conserved Sequence; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D017421:Sequence Analysis; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000378:metabolism; D013912:Threonine / Q000378:metabolism
D009687:Nuclear Proteins; D013912:Threonine; D012694:Serine; D064413:3-Phosphoinositide-Dependent Protein Kinases; C578562:PDPK1 protein, human; D017346:Protein Serine-Threonine Kinases