A novel transmembrane Ser/Thr kinase complexes with protein phosphatase-1 and inhibitor-2.
Protein kinases and protein phosphatases exert coordinated control over many essential cellular processes. Here, we describe the cloning and characterization of a novel human transmembrane protein KPI-2 (Kinase/Phosphatase/Inhibitor-2) that was identified by yeast two-hybrid using protein phosphatase inhibitor-2 (Inh2) as bait. KPI-2 mRNA was predominantly expressed in skeletal muscle. KPI-2 is a 1503-residue protein with two predicted transmembrane helices at the N terminus, a kinase domain, followed by a C-terminal domain. The transmembrane helices were sufficient for targeting proteins to the membrane. KPI-2 kinase domain has about 60% identity with its closest relative, a tyrosine kinase. However, it only exhibited serine/threonine kinase activity in autophosphorylation reactions or with added substrates. KPI-2 kinase domain phosphorylated protein phosphatase-1 (PP1C) at Thr(320), which attenuated PP1C activity. KPI-2 C-terminal domain directly associated with PP1C, and this required a VTF motif. Inh2 associated with KPI-2 C-terminal domain with and without PP1C. Thus, KPI-2 is a kinase with sites to associate with PP1C and Inh2 to form a regulatory complex that is localized to membranes.
Wang
Hong
H
Center for Cell Signaling, University of Virginia School of Medicine, Charlottesville, VA 22908-0577, USA.
Brautigan
David L
DL
D020816:Amino Acid Motifs; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D019556:COS Cells; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005982:Glutathione Transferase / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D054645:Protein Phosphatase 1; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D011817:Rabbits; D011994:Recombinant Proteins / Q000378:metabolism; D013912:Threonine / Q000378:metabolism; D014018:Tissue Distribution; D014162:Transfection; D020798:Two-Hybrid System Techniques; D000097847:Protein Phosphatase Inhibitory Proteins
D018076:DNA, Complementary; D005982:Glutathione Transferase; D008565:Membrane Proteins; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D017346:Protein Serine-Threonine Kinases; D011506:Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D013912:Threonine; C024833:protein phosphatase inhibitor-2; D000097847:Protein Phosphatase Inhibitory Proteins; C470798:LMTK2 protein, human