Regulation of connexin 36 expression during development.

In the mammalian CNS, the expression of neuronal gap junction protein, connexin 36 (Cx36), increases during the first 2 weeks of postnatal development and then decreases during the following 2 weeks. Recently we showed that the developmental increase in Cx36 expression is augmented by chronic (2 weeks) activation of group II metabotropic glutamate receptors (mGluR), prevented by chronic receptor inactivation, and the receptor-dependent increase in Cx36 expression is regulated via transcriptional control of the Cx36 gene activity. We demonstrate here that acute (60 min) activation of group II mGluRs in developing cortical neuronal cultures causes transient increase in Cx36 protein expression with decrease during the following 24h. However, there is no change in Cx36 mRNA expression. In addition, the data indicate that transient increase in Cx36 expression is due to new protein synthesis. The results suggest that, during development, acute activation of group II mGluRs causes up-regulation of Cx36 via post-transcriptional mechanisms. However, if the receptor activation is sustained, transcriptional activation of the Cx36 gene occurs.