Distinct modulation of a gene expression of the type 1 and 2 IP3 receptors by retinoic acid in brain areas

Inositol 1,4,5-trisphosphate (IP3) receptors belong to the intracellular calcium channels that release calcium from the intracellular stores after binding IP3. Three types of IP3 receptors occurred in a tissue specific manner and different promoters direct their gene expression. Thus, understanding of the transcriptional regulation is the first step towards comprehension of the function of these receptors. Since the retinoic acid activates RARE and AP2 transcription factors, the present study focuses on determination of whether or not expression of type 1 and 2 IP3 receptors is modulated by retinoic acid in selected brain areas. We have found that mRNA levels of the type 1 IP3 receptors were decreased significantly in cerebellum and hypothalamus, but not in the brain stem of rats treated with retinoic acid, compared to untreated littermates. The mRNA levels of the type 2 IP3 receptor were significantly decreased in all tested tissues, cerebellum, hypothalamus, and also in brain stem after the treatment with retinoic acid. These results show that gene expression of both type 1 and 2 IP3 receptors is regulated by retinoic acid, although the effect of retinoic acid on mRNA levels of the type 1 IP3 receptors is dependent on brain area.