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Expression of Nerve Membrane Proteins in a Naturally Occurring Ca 2+ Channelopathy
Author(s) -
ColónCarrion Nicole,
ColónRodriguez Alexandra,
Atchison William D.
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.1188.5
Subject(s) - voltage dependent calcium channel , medicine , receptor , endocrinology , calcium channel , forebrain , downregulation and upregulation , p type calcium channel , biology , cerebellum , protein subunit , microbiology and biotechnology , chemistry , gabaa receptor , l type calcium channel , t type calcium channel , calcium , genetics , gene , central nervous system
Neuronal voltage gated calcium channels (VGCC) are essential for numerous cellular functions including synaptogenesis and neurotransmitter release. Mutations in individual subunits of the VGCC are known to result in many neurological disorders. In tottering ( tg ) mice, the mutation in the α 1A subunit of the P/Q calcium channel leads to ataxia and motor seizures that result in absence epilepsy in humans. Studies done with tg mice have also implied that GABA A receptor function is impaired. Consequently, we compared the expression of GABA A receptor subunits and VGCC subunits in the forebrain (FB), which is not a specific target of the tg mutation with that in the cerebellum (CB), which is a primary target. Previous functional studies have shown that Ca 2+ channels subtypes such as the L and N type are upregulated and the inhibitory GABA A receptor expression is decreased in the CB of tg mice. Our hypothesis was that gene expression of L, N, R, & T type VGCCs will be upregulated and certain GABA A receptors subunits specific to CB will be downregulated in the CB and not the FB of tg mice. QPCR was performed on reverse transcript (cDNA) of RNA isolated from CB and FB tissue of 6mo old male wt, heterozygote (+/−) and homozygote (+/+) tg mice. VGCC α 1A (P/Q type), α 1B (N type), α 1C (L type), α 1E (R type), β1, β2, β3, and β4 subunits as well as GABA A α1, α6, β1, β3, γ2 and δ subunit expression was measured in CB and FB of mice. In the CB α 1A , α 1B , α 1C , α 1E subunit of the (+/−) tg mice were at control levels. The (+/+) tg mice showed a downregulation of the α 1A , as expected, and an upregulation of the α 1B . This suggests that the α 1B subunit is compensating for the loss of α 1A subunit expression as it has been shown previously. In the FB, (+/−) tg mice had all α1 subunits expressed similar to control, while the (+/+) tg mice displayed a downregulation. In the CB the β3 subunit for the (+/−) tg mice was upregulated. In the FB the β subunits were upregulated for the (+/−) tg mice, and no significant change was observed for the (+/+) tg mice. Expression of GABA A α1, α6, γ2 and δ was increased in the CB of (+/−) and (+/+) tg mice. However in the FB there was no significant difference in expression of GABA A receptor subunits in the (+/−) compared to control; there was a downregulation of the γ2 subunit in the (+/+) tg mice. Our results demonstrate that VGCC and GABA A receptor subunit expression is altered as a result of the homozygous mutation of the α 1A subunit of the VGCC. These results suggest that alterations in expression of these nerve membrane proteins can be contributing to the observed alterations in synaptic transmission and phenotypic changes observed in the tg mouse model. Support or Funding Information Supported by NIH NIEHS grants R25ES025060, T32ES007255 and R01ES024064.