The role of the novel putative stargazin-like γ-subunits in relation to voltage-gated calcium channel function is controversial. We have previously cloned a member of this family, γ7, and found that it markedly reduced functional expression of CaV2.2 channels. Here we have identified the novel mechanism for this suppression: it results from a 2-fold increase in the CaV2.2 mRNA degradation rate. After 9 hours with Actinomycin D, rabbit CaV2.2 mRNA in Xenopus ooytes is reduced by 54.2 ± 14% under control conditions and by 88.1 ± 3.6% in the presence of human γ7, n = 11 and 7, respectively (mean±SEM, P<0.05, Student's t test). The half-life of CaV2.2 mRNA was then estimated to be 7.8 h under control conditions and 3.5 h in the presence of γ7. This process regulates the physiological level of CaV2.2 transcripts, since knockdown of endogenous γ7 with short hairpin RNA constructs in the neuron-like PC12 cell line markedly increased their endogenous CaV2.2 mRNA level. Physiologically, γ7 mRNA is down-regulated following differentiation of these cells. As the removal of the cytoplasmic C-terminus of γ7 induces the loss of function of γ7, this part of the protein is essential for all its effects. The RNA binding-protein hnRNPA2 is an endogenous binding partner determined by immunoprecipitation and proteomic identification. CaV2.2 mRNA binds to hnRNPA2 via its A2RE sequences. Our results support the hypothesis that CaV2.2 mRNA is targeted for degradation by γ7, via binding to hnRNPA2.
University College London 2006 (2006) Proc Physiol Soc 3, C36
Oral Communications: Regulation of N-type calcium channel transcript stability by the stargazin-related protein gamma 7
Laurent Ferron1, David J Cox1, Jerome Leroy1, Karen M Page1, Manuela Nieto-Rostro1, Steven Bolsover2, Adrian J Butcher1, Anthony Davies1, Priya Sellaturay1<
1. Department of Pharmacology, University College London, London, United Kingdom. 2. Department of Physiology, University College London, London, United Kingdom.
View other abstracts by:
Where applicable, experiments conform with Society ethical requirements.