Protein & Peptide Letters

Prof. Ben M. Dunn  
Department of Biochemistry and Molecular Biology
University of Florida
College of Medicine
P.O. Box 100245
Gainesville, FL
USA
Email: bdunn@ufl.edu

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Hypoxia Upregulates MAPKp38/MAPKERK Phosphorylation In Vitro: Neuroimmunological Differential Time-Dependent Expression of MAPKs

Author(s): John J. Haddad and Lama B. Hanbali

Affiliation: Department of Medical Laboratory Technology, Faculty of Health Sciences, Beirut Arab University, Beirut, Lebanon.

Keywords: Anaerobiosis, anoxia, cortical neurons, hippocampal slices, hypoxia, MAPKs, neuroprotection, phosphorylation.

Abstract:

In mammalian cells, responses to hypoxia at the molecular transduction level are hallmarks of adaptation and survival under oxygen deprivation conditions. In this study, the protein expression patterns of mitogen-activated protein kinases (MAPKs) are investigated under hypoxia in primary cortical neurons and in a model of organotypic hippocampal slices in neonatal Sprague-Dawley rats. Abrupt fluctuations in MAPK expression can occur during anoxia, hypoxia, and relative hyperoxic shifts (e.g., reoxygenation); therefore, phosphorylation and dephosphorylation states could be crucial factors in metabolic reorganization for withstanding anaerobiosis. Whole cellular protein extracts were analyzed for the phosphorylation of MAPKpp38 and MAPKERK-1/2 (p44/p42) at threonine and tyrosine residues (Thr180/Tyr182) at different time periods of hypoxic exposure relative to a fixed normoxia control. The phospho-MAPKp38 (p-MAPKp38) to MAPKp38 relative unit ratio revealed that MAPKp38 expression increased in cortical neurons after 5 and 10 min, but decreased abruptly afterwards (20 – 120 min). The expression of phospho-MAPKERK-1 (p-MAPKERK-1/p44), however, decreased whereas that of p-MAPKERK-2/p42 increased compared to normoxia. In rat hippocampal slices (RHS), the expression of p-MAPKp38 was slightly but significantly higher in hypoxia, whereas the expression of p-MAPKERK-2/p42 increased and that of p-MAPKERK-1/p44 was intangible. This indicates that in cortical neurons hypoxia differentially upregulated the phosphorylation activation states of MAPKp38 and MAPKERK-1/2 (p44/p42), whereas in the RHS model MAPKp38 and MAPKERK-2/p42, but not MAPKERK-1/p44, phosphorylation states were upregulated in response to hypoxia. The neuroimmunological molecular patterns of the differential MAPK phosphorylation in vitro and ex vivo in response to hypoxic shift indicated a significant role for these kinases in cellular adaptation to oxygen deprivation, and thereby may identify physiologic and neuroprotective responsive signaling cofactors and pathways in cortical and hippocampal neurons during hypoxia.

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Article Details

VOLUME: 21
ISSUE: 5
Page: [444 - 451]
Pages: 8
DOI: 10.2174/092986652105140218112521