The Dictyostelium Mitogen-activated Protein Kinase ERK2 Is Regulated by Ras and cAMP-dependent Protein Kinase (PKA) and Mediates PKA Function

doi:10.1074/jbc.272.7.3883

The Dictyostelium Mitogen-activated Protein Kinase ERK2 Is Regulated by Ras and cAMP-dependent Protein Kinase (PKA) and Mediates PKA Function*

From the ^‡ Department of Biology, Center for Molecular Genetics, University of California, San Diego, La Jolla, California 92093-0634, the
^‡‡ Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, and the
** MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, United Kingdom

^§§ To whom correspondence should be addressed:
Center for Molecular Genetics, Rm. 225, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093-0634.
Tel.: 619-534-2788; Fax: 619-534-7073; E-mail: rafirtel{at}ucsd.edu

Abstract

The chemoattractant cAMP, acting through serpentine cAMP receptors, results in a rapid and transient stimulation of the Dictyostelium mitogen-activated protein kinase ERK2 activity (1). In this study we show that other pathways required for aggregation, including Ras and cAMP-dependent protein kinase (PKA), are important regulators of ERK2 activation and adaptation. By examining both the level and kinetics of activation and adaptation of ERK2, we show that Ras is a negative regulator of ERK2. Activated Ras or disruption of a Ras GAP gene results in reduced ERK2 activation whereas disruption of putative Ras GEF or expression of dominant negative Ras proteins have a more rapid, higher, and extended activation. CRAC, a PH domain-containing protein required for adenylyl cyclase activation, is also required for proper ERK2 adaptation. PKA overexpression results in a more rapid, higher level of activation, whereas pka null cells show a lower level but more extended ERK2 activation. Furthermore, we show that constitutive expression of PKA catalytic subunit bypasses the requirement of ERK2 for aggregation and later development, indicating that PKA lies downstream from ERK2 and that ERK2 may regulate one or more components of the signaling pathway required for mediating PKA function, possibly by directly regulating PKA R or a protein controlling the intracellular level of cAMP.

Footnotes

↵^¶ Supported by Fondation pour la Recherche Medicale de France and Human Frontiers Science Program fellowships.
↵^§ These two authors contributed equally to this manuscript.
↵^∥ Supported in part Grant-in-aid for Scientific Research 06044234 from the Ministry of Education, Science, and Culture of Japan. Present address: Department of Biology, Faculty of Science, Osaka University, Toyonaka, Osaka 560, Japan.
↵* This work was supported by United States Public Health Service Grants GM28007 (to P. N. D.) and GM37830 (to R. A. F.). 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:

cAR

chemoattractant receptor

MAP

mitogen-activated protein

ACA

adenylyl cyclase

CRAC

cytosolic regulator of adenylyl cyclase

PKA

cAMP-dependent protein kinase

GEF

guanine exchange factor

MBP

myelin basic protein

GTPγS

guanosine 5′-3-O-(thio)triphosphate.
↵² M. Maeda and R. A. Firtel, unpublished observations.
↵³ M. Maeda, L. Aubry, and R. A. Firtel, manuscript in preparation.
- Received December 5, 1996.