Inositol 1,4,5-trisphosphate receptors: distinct neuronal and nonneuronal forms derived by alternative splicing differ in phosphorylation.

We have identified two distinct transcripts of inositol 1,4,5-trisphosphate receptor by using the PCR on first-strand cDNAs from various rat tissues. The longer form, corresponding to the previously cloned adult rat brain inositol 1,4,5-trisphosphate receptor, contains a 120-nucleotide insert between the two cAMP-dependent protein kinase phosphorylation consensus sequences. The shorter form (lacking the insert) predominates in fetal brain and peripheral tissues and appears to represent a nonneuronal receptor, whereas the longer form is found in adult brain and appears to be exclusively neuronal. The phosphorylation kinetics by cAMP-dependent protein kinase and the phosphopeptide maps differ for inositol 1,4,5-trisphosphate receptors purified from tissues predominantly expressing different forms of the transcript. IMAGES: