Negative regulation of a protein tyrosine phosphatase by tyrosine phosphorylation.
The low molecular weight protein tyrosine phosphatase (LMW-PTP) is a ubiquitously expressed enzyme with several proposed roles in cell signaling. Previously, two tyrosine phosphorylation modifications of LMW-PTP at sites Tyr-131 and Tyr-132 in response to growth factor stimulation have been mapped and suggested to stimulate LMW-PTP phosphatase activity. Biochemical analysis of tyrosine phosphorylation of a tyrosine phosphatase is challenging because of the intrinsic instability of these modifications. Here we used expressed protein ligation to site-specifically incorporate a phosphotyrosine mimic (phosphonomethylenephenylalanine, Pmp) at the Tyr-131 and Tyr-132 positions and measured the catalytic activity of these semisynthetic LMW-PTPs. The phosphonate-modified LMW-PTPs were 10- to 23-fold less active in dephosphorylating phosphotyrosine peptides derived from the PDGF receptor and p190RhoGap, two putative cellular substrates. These findings suggest the first example of a tyrosine phosphatase that is inhibited by tyrosine phosphorylation and provide a new model for the regulation of LMW-PTP and its role in cell adhesion.
Schwarzer
Dirk
D
Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Zhang
Zhongsen
Z
Zheng
Weiping
W
Cole
Philip A
PA
D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009596:Nitrophenols / Q000737:chemistry / Q000378:metabolism; D009943:Organophosphorus Compounds / Q000737:chemistry / Q000378:metabolism; D010766:Phosphorylation; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry* / Q000378:metabolism*; D017479:Receptors, Platelet-Derived Growth Factor / Q000737:chemistry / Q000378:metabolism; D014443:Tyrosine / Q000737:chemistry / Q000378:metabolism
D009596:Nitrophenols; D009943:Organophosphorus Compounds; C008644:nitrophenylphosphate; D014443:Tyrosine; D017479:Receptors, Platelet-Derived Growth Factor; D017027:Protein Tyrosine Phosphatases