alpha2-chimaerin, a Cdc42/Rac1 regulator, is selectively expressed in the rat embryonic nervous system and is involved in neuritogenesis in N1E-115 neuroblastoma cells.

Abstract

Neuronal differentiation involves Rac and Cdc42 GTPases. alpha-Chimaerin, a Rac/Cdc42 regulator, occurs as alpha1- and alternatively spliced Src homology 2 (SH2) domain-containing alpha2-isoforms. alpha2-chimaerin mRNA was highly expressed in the rat embryonic nervous system, especially in early postmitotic neurons. alpha1-chimaerin mRNA was undetectable before embryonic day 16.5. Adult alpha2-chimaerin mRNA was restricted to neurons within specific brain regions, with highest expression in the entorhinal cortex. alpha2-chimaerin protein localized to neuronal perikarya, dendrites, and axons. The overall pattern of alpha2-chimaerin mRNA expression resembles that of cyclin-dependent kinase regulator p35 (CDK5/p35) which participates in neuronal differentiation and with which chimaerin interacts. To determine whether alpha2-chimaerin may have a role in neuronal differentiation and the relevance of the SH2 domain, the morphological effects of both chimaerin isoforms were investigated in N1E-115 neuroblastoma cells. When plated on poly-lysine, transient alpha2-chimaerin but not alpha1-chimaerin transfectants formed neurites. Permanent alpha2-chimaerin transfectants generated neurites whether or not they were stimulated by serum starvation, and many cells were enlarged. Permanent alpha1-chimaerin transfectants displayed numerous microspikes and contained F-actin clusters, a Cdc42-phenotype, but generated few neurites. In neuroblastoma cells, alpha2-chimaerin was predominantly soluble with some being membrane-associated, whereas alpha1-chimaerin was absent from the cytosol, being membrane- and cytoskeleton-associated, paralleling their subcellular distribution in brain. Transient transfection with alpha2-chimaerin mutated in the SH2 domain (N94H) generated an alpha1-chimaerin-like phenotype, protein partitioned in the particulate fraction, and in NGF-stimulated pheochromocytoma cell line 12 (PC12) cells, neurite formation was inhibited. These results indicate a role for alpha2-chimaerin in morphological differentiation for which its SH2 domain is vital.

• Authors: C Hall, G J Michael, N Cann, G Ferrari, M Teo, T Jacobs, C Monfries, L Lim
• Journal: The Journal of neuroscience : the official journal of the Society for Neuroscience (J Neurosci) Vol. 21 Issue 14 Pg. 5191-202 (Jul 15 2001) ISSN: 1529-2401 [Electronic] United States
• PMID: 11438594 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Chimerin 1
• Protein Isoforms
• RNA, Messenger
• cdc42 GTP-Binding Protein
• rac1 GTP-Binding Protein

Topics

• Aging (metabolism)
• Alternative Splicing (genetics)
• Animals
• COS Cells
• Cell Differentiation (drug effects, physiology)
• Chimerin 1 (analysis, biosynthesis, genetics)
• Entorhinal Cortex (metabolism)
• In Situ Hybridization
• Mice
• Mutagenesis, Site-Directed
• Nervous System (chemistry, embryology, growth & development, metabolism)
• Neurites (metabolism)
• Neuroblastoma (metabolism)
• Organ Specificity
• PC12 Cells
• Protein Isoforms (biosynthesis, genetics)
• RNA, Messenger (metabolism)
• Rats
• Rats, Sprague-Dawley
• Subcellular Fractions (chemistry)
• Transfection
• cdc42 GTP-Binding Protein (metabolism)
• rac1 GTP-Binding Protein (metabolism)
• src Homology Domains (physiology)