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.
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.
Hall
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Department of Neurochemistry, Institute of Neurology, University College London, London WC1N 1PJ, United Kingdom.
Michael
G J
GJ
Cann
N
N
Ferrari
G
G
Teo
M
M
Jacobs
T
T
Monfries
C
C
Lim
L
L
D000375:Aging / Q000378:metabolism; D017398:Alternative Splicing / Q000235:genetics; D000818:Animals; D019556:COS Cells; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D020848:Chimerin 1 / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D018728:Entorhinal Cortex / Q000378:metabolism; D017403:In Situ Hybridization; D051379:Mice; D016297:Mutagenesis, Site-Directed; D009420:Nervous System / Q000737:chemistry / Q000196:embryology / Q000254:growth & development / Q000378:metabolism*; D016501:Neurites / Q000378:metabolism*; D009447:Neuroblastoma / Q000378:metabolism; D009928:Organ Specificity; D016716:PC12 Cells; D020033:Protein Isoforms / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013347:Subcellular Fractions / Q000737:chemistry; D014162:Transfection; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*; D018909:src Homology Domains / Q000502:physiology
D020848:Chimerin 1; D020033:Protein Isoforms; D012333:RNA, Messenger; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein