Components of a New Human Protein Kinase Signal Transduction Pathway

doi:10.1074/jbc.270.21.12665

Components of a New Human Protein Kinase Signal Transduction Pathway (*)

From the (1) Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0606

^§ To whom correspondence should be addressed:
Dept. of Biological Chemistry, University of Michigan Medical School, Rm. 5416, Medical Science I, Ann Arbor, MI 48109-0606.
Tel.: 313-764-8192; Fax: 313-763-4581.

Abstract

We have identified two components of a new protein kinase signaling cascade, MAPK/ERK kinase 5 (MEK5) and extracellular signal-regulated kinase 5 (ERK5). The MEK5 cDNA was isolated by degenerate PCR and encodes a 444-amino acid protein, which has approximately 40% identity to known MEKs. ERK5 was identified by a specific interaction with the MEK5 mutants S311A/T315A and K195M in the yeast two-hybrid system. The proteins were found to interact in an in vitro binding assay as well. ERK5 did not interact with MEK1 or MEK2. ERK5 is predicted to contain 815 amino acids and is approximately twice the size of all known ERKs. The C terminus of ERK5 has sequences which suggest that it may be targeted to the cytoskeleton. Sequences located in the N terminus of MEK5 may be important in coupling GTPase signaling molecules to the MEK5 protein kinase cascade. Both MEK5 and ERK5 are expressed in many adult tissue and are abundant in heart and skeletal muscle. A recombinant GST-ERK5 kinase domain displays autophosphorylation on Ser/Thr and Tyr residues.

Footnotes

↵* This work was supported by National Institutes of Health NIDDKD Grant 18024 and a postdoctoral fellowship from the American Diabetes Association (to G. Z.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank/EMBL Data Bank with accession number(s) U25265 and U25278.
↵¹ The abbreviations used are:

ERK

extracellular-regulated kinase

MAP

mitogen-activated protein

MAPK

MAP kinase

MAPKK or MKK

MAP kinase kinase

MEK

MAPK/ERK kinase

JNK

c-Jun N-terminal kinase

kb

kilobase pair(s)

PCR

polymerase chain reaction

PAGE

polyacrylamide gel electrophoresis

GST

glutathione S-transferase.
↵²ERK is also referred to as mitogen-activated protein kinase (MAPK) in the literature. We will employ the ERK nomenclature.
↵³MEK is also referred to as mitogen-activated protein kinase kinase (MAPKK or MKK) in the literature. We will employ the MEK nomenclature.
↵⁴JNK is also referred to as stress-activated protein kinase (SAPK) in the literature.