Activation of Myosin-I by Members of the Ste20p Protein Kinase Family

doi:10.1074/jbc.271.50.31787

Activation of Myosin-I by Members of the Ste20p Protein Kinase Family*

From the ^¶ Eukaryotic Genetics Group, Biotechnology Research Institute, National Research Council of Canada, Montreal, Quebec H4P 2R2, Canada, and the
^∥ Department of Biochemistry, Queen's University, Kingston, Ontario K7L 3N6, Canada

^″ To whom correspondence should be addressed:
Eukaryotic Genetics Group, Biotechnology Research Institute, National Research Council of Canada, 6100 Royalmount Ave., Montreal, Quebec H4P 2R2, Canada.
Tel.: 514-496-6358; Fax: 514-496-6213; E-mail: EKKEHARD.LEBERER{at}NRC.CA.

Abstract

The heavy chain of myosin-ID isolated from Dictyostelium was identified as an in vitro substrate for members of the Ste20p family of serine/threonine protein kinases which are thought to regulate conserved mitogen-activated protein kinase pathways. Yeast Ste20p and Cla4p and mammalian p21-activated protein kinase (PAK) phosphorylated the heavy chain to 0.5-0.6 mol of P_i/mol and stimulated the actin-dependent Mg²⁺-ATPase activity to an extent equivalent to that of the Ste20p-like myosin-I heavy chain kinase isolated from Dictyostelium. PAK purified from rat brain required GTPγS-Cdc42 to express full activity, whereas recombinant mouse mPAK3 fused to glutathione S-transferase and purified from bacteria, and Ste20p and Cla4p purified from yeast extracts were fully active without GTPγS-Cdc42. These results suggest, together with the high degree of structural and functional conservation of Ste20p family members and myosin-I isoforms, that myosin-I activation by Ste20p family protein kinases may contribute to the regulation of morphogenetic processes in organisms ranging from yeast to mammalian cells.

Footnotes

↵* This work was supported by the National Research Council (NRC) of Canada, the Medical Research Council of Canada, and the Heart and Stroke Foundation of Ontario. The NRC publication number for this work is 39939. 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.
↵¹ The abbreviations used are:

MAP

mitogen-activated protein

GST

glutathione S-transferase

MIHCK

myosin-I heavy chain kinase

PAK

p21-activated protein kinase

mPAK3

mouse PAK3 isoform

PAGE

polyacrylamide gel electrophoresis

rPAK

rat brain PAK

GTPγS

guanosine 5′-3-O-(thio)triphosphate.
↵² C. Wu, V. Lytvyn, D. Y. Thomas, and E. Leberer, unpublished observations.
- Received September 24, 1996.