Regulation of SHP-1 tyrosine phosphatase in human platelets by serine phosphorylation at its C terminus.
SHP-1 is a Src homology 2 (SH2) domain-containing tyrosine phosphatase that plays an essential role in negative regulation of immune cell activity. We describe here a new model for regulation of SHP-1 involving phosphorylation of its C-terminal Ser591 by associated protein kinase Calpha. In human platelets, SHP-1 was found to constitutively associate with its substrate Vav1 and, through its SH2 domains, with protein kinase Calpha. Upon activation of either PAR1 or PAR4 thrombin receptors, the association between the three proteins was retained, and Vav1 became phosphorylated on tyrosine and SHP-1 became phosphorylated on Ser591. Phosphorylation of SHP-1 was mediated by protein kinase C and negatively regulated the activity of SHP-1 as demonstrated by a decrease in the in vitro ability of SHP-1 to dephosphorylate Vav1 on tyrosine. Protein kinase Calpha therefore critically and negatively regulates SHP-1 function, forming part of a mechanism to retain SHP-1 in a basal active state through interaction with its SH2 domains, and phosphorylating its C-terminal Ser591 upon cellular activation leading to inhibition of SHP-1 activity and an increase in the tyrosine phosphorylation status of its substrates.
Department of Pharmacology, School of Medical Sciences, University Walk, Bristol BS8 1TD, United Kingdom.
Matthew L
ML
Jones
Johnathan D
JD
Craik
Jonathan M
JM
Gibbins
Alastair W
AW
Poole
D000595:Amino Acid Sequence; D001792:Blood Platelets / Q000201:enzymology*; D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D005786:Gene Expression Regulation; D015971:Gene Expression Regulation, Enzymologic; D005982:Glutathione Transferase / Q000378:metabolism; D049452:Green Fluorescent Proteins; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008164:Luminescent Proteins / Q000737:chemistry / Q000378:metabolism; D018613:Microscopy, Confocal; D008954:Models, Biological; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D015513:Oncogene Proteins / Q000378:metabolism; D010766:Phosphorylation; D011233:Precipitin Tests; D011493:Protein Kinase C / Q000378:metabolism; D051571:Protein Kinase C-alpha; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000096:biosynthesis* / Q000235:genetics; D051567:Proto-Oncogene Proteins c-vav; D044463:Receptor, PAR-1 / Q000378:metabolism; D018179:Receptors, Thrombin / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000737:chemistry / Q000378:metabolism*; D013379:Substrate Specificity; D013917:Thrombin / Q000737:chemistry; D014443:Tyrosine / Q000737:chemistry; D018909:src Homology Domains
D047908:Intracellular Signaling Peptides and Proteins; D008164:Luminescent Proteins; D015513:Oncogene Proteins; D051567:Proto-Oncogene Proteins c-vav; D044463:Receptor, PAR-1; D018179:Receptors, Thrombin; D011993:Recombinant Fusion Proteins; C496618:VAV1 protein, human; D049452:Green Fluorescent Proteins; D014443:Tyrosine; D012694:Serine; D005982:Glutathione Transferase; C496628:PRKCA protein, human; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; C509249:PTPN6 protein, human; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; D013917:Thrombin; C112908:protease-activated receptor 4