Exp Mol Med.  2000 Mar;32(1):47-51.

Regulation of chicken protein tyrosine phosphatase 1 and human protein tyrosine phosphatase 1B activity by casein kinase II- and p56lck-mediated phosphorylation

• Kang KR
• Kim CW

Abstract

Protein tyrosine phosphorylation and dephosphorylation are important in the regulation of cell proliferation and signaling cascade. In order to examine whether phosphatase activity of CPTP1 and HPTP1B, typical nontransmembrane protein tyrosine phosphatase, could be controlled by phosphorylation, affinity-purified PTPs were phosphorylated by CKII and p56lck in vitro. Phosphoamino acid analysis revealed that CPTP1 was phosphorylated on both serine and threonine residues by CKII, and tyrosine residue by p56lck. Phosphatase activity of CPTP1 was gradually increased by three-fold concomitant with phosporylation by CKII. Phosphorylation of HPTP1B by CKII resulted in quick two-fold enhancement of its phosphatase activity within 5 min of incubation and remained in that state. In the presence of CKII inhibitor, heparin or poly(Glu.Tyr), both phosphorylation and enhancement of phosphatase activity of CPTP1 and HPTP1B were mostly blocked. p56lck catalyzed tyrosine phosphorylation of CPTP1 and HPTP1B was only observed by inhibiting the intrinsic tyrosine phosphatase activity. Taken together, these results indicate that CPTP1 or HPTP1B possesses a capability to regulate its phosphatase activity through phosphorylation processes and may participate in the cellular signal cascades.

Keyword

protein tyrosine phosphatase; CKII; p56 lck; phosphorylation

MeSH Terms

Adenosine Triphosphate/metabolism
Animal
Chickens
Dose-Response Relationship, Drug
Heparin/pharmacology
Human
Hydrogen Peroxide/pharmacology
Lymphocyte Specific Protein Tyrosine Kinase p56(lck)/metabolism*
Peptides/pharmacology
Phosphorus Radioisotopes/diagnostic use
Phosphorylation/drug effects
Protein-Serine-Threonine Kinases/metabolism*
Protein-Tyrosine-Phosphatase/metabolism*
Tyrosine/metabolism
Vanadates/pharmacology