Journal article
Insulin stimulation of a MEK-dependent but ERK-independent SOS protein kinase
Molecular and cellular biology, Vol.16(2), pp.577-583
02/1996
DOI: 10.1128/MCB.16.2.577
PMCID: PMC231036
PMID: 8552085
Abstract
The Ras guanylnucleotide exchange protein SOS undergoes feedback phosphorylation and dissociation from Grb2 following insulin receptor kinase activation of Ras. To determine the serine/threonine kinase(s) responsible for SOS phosphorylation in vivo, we assessed the role of mitogen-activated, extracellular-signal-regulated protein kinase kinase (MEK), extracellular-signal-regulated protein kinase (ERK), and the c-JUN protein kinase (JNK) in this phosphorylation event. Expression of a dominant-interfering MEK mutant, in which lysine 97 was replaced with arginine (MEK/K97R), resulted in an inhibition of insulin-stimulated SOS and ERK phosphorylation, whereas expression of a constitutively active MEK mutant, in which serines 218 and 222 were replaced with glutamic acid (MEK/EE), induced basal phosphorylation of both SOS and ERK. Although expression of the mitogen-activated protein kinase-specific phosphatase (MKP-1) completely inhibited the insulin stimulation of ERK activity both in vitro and in vivo, SOS phosphorylation and the dissociation of the Grb2-SOS complex were unaffected. In addition, insulin did not activate the related protein kinase JNK, demonstrating the specificity of insulin for the ERK pathway. The insulin-stimulated and MKP-1-insensitive SOS-phosphorylating activity was reconstituted in whole-cell extracts and did not bind to a MonoQ anion-exchange column. In contrast, ERK1/2 protein was retained by the MonoQ column, eluted with approximately 200 mM NaCl, and was MKP-1 sensitive. Although MEK also does not bind to MonoQ, immunodepletion analysis demonstrated that MEK is not the insulin-stimulated SOS-phosphorylating activity. Together, these data demonstrate that at least one of the kinases responsible for SOS phosphorylation and functional dissociation of the Grb2-SOS complex is an ERK-independent but MEK-dependent insulin-stimulated protein kinase.
Details
- Title: Subtitle
- Insulin stimulation of a MEK-dependent but ERK-independent SOS protein kinase
- Creators
- Kathleen H Holt - Department of Physiology & Biophysics, University of Iowa, Iowa City 52242-1109, USABarry G Kasson - Department of Physiology & Biophysics, University of Iowa, Iowa City 52242-1109, USAJeffrey E Pessin - Department of Physiology & Biophysics, University of Iowa, Iowa City 52242-1109, USA
- Resource Type
- Journal article
- Publication Details
- Molecular and cellular biology, Vol.16(2), pp.577-583
- DOI
- 10.1128/MCB.16.2.577
- PMID
- 8552085
- PMCID
- PMC231036
- NLM abbreviation
- Mol Cell Biol
- ISSN
- 0270-7306
- eISSN
- 1098-5549
- Language
- English
- Date published
- 02/1996
- Academic Unit
- Neuroscience and Pharmacology
- Record Identifier
- 9984040586002771
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