The CLK Family Kinases, CLK1 and CLK2, Phosphorylate and Activate the Tyrosine Phosphatase, PTP-1B

doi:10.1074/jbc.274.38.26697

The CLK Family Kinases, CLK1 and CLK2, Phosphorylate and Activate the Tyrosine Phosphatase, PTP-1B*

From the Departments of Neurology and Neurosciences and the Alzheimer Research Laboratory, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106

Abstract

The protein-tyrosine phosphatase PTP-1B is an important regulator of intracellular protein tyrosine phosphorylation, and is itself regulated by phosphorylation. We report that PTP-1B and its yeast analog, YPTP, are phosphorylated and activated by members of the CLK family of dual specificity kinases. CLK1 and CLK2 phosphorylation of PTP-1B in vitro activated the phosphatase activity approximately 3–5-fold using eitherp-nitrophenol phosphate, or tyrosine-phosphorylated myelin basic protein as substrates. Co-expression of CLK1 or CLK2 with PTP-1B in HEK 293 cells led to a 2-fold stimulation of phosphatase activityin vivo. Phosphorylation of PTP-1B at Ser⁵⁰ by CLK1 or CLK2 is responsible for its enzymatic activation. These findings suggest that phosphorylation at Ser⁵⁰ by serine threonine kinases may regulate the activation of PTP-1B in vivo. We also show that CLK1 and CLK2 phosphorylate and activate the S. cerevisiae PTP-1B family member, YPTP1. CLK1 phosphorylation of YPTP1 led to a 3-fold stimulation of phosphatase activity in vitro. We demonstrate that CLK phosphorylation of Ser⁸³ on YPTP1 is responsible for the activation of this enzyme. These findings demonstrate that the CLK kinases activate PTP-1B family members, and this phosphatase may be an important cellular target for CLK action.

Footnotes

↵* This work was supported by National institutes of Health Grant NS31987.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵‡ To whom correspondence should be addressed: Alzheimer Research Laboratory, E504, Case Western Reserve University School of Medicine, 10900 Euclid Ave., Cleveland, OH 44106. Tel.: 216-368-6101; Fax: 216-368-3079; E-mail: gel2@po.cwru.edu.
↵2 H. Menegay, F. Moeslein, and G. Landreth, submitted for publication.
↵3 F. M. Moeslein, M. P. Myers, and G. E. Landreth, unpublished data.
Abbreviations:

EGF

epidermal growth factor

BSA

bovine serum albumin

TBS

Tris-buffered saline

GST

glutathione S-transferase

PAGE

polyacrylamide gel electrophoresis

ERK

extracellular signal-regulated kinase

PNPP

p-nitrophenol phosphate

MBP

myelin basic protein
- Received December 2, 1998.
- Revision received July 1, 1999.
The American Society for Biochemistry and Molecular Biology, Inc.