The lens: Demonstration that Ca + calmodulin control cAMP synthesis

cAMP-dependent protein kinase (cAMP-PK) and major membrane substrates for this enzyme have now been identified in the bovine lens. To study the regulation of cAMP synthesis in the lens, the authors first separated lenses into nuclear (N) and cortical (C) regions. In response to changes in the intracellular Ca super(2+) concentration cAMP is synthesized in the lens C but not the N regions. This AC activity also appears to be regulated by calmodulin. That the mambrane substrates for cAMP-PK are present in all regions of the lens indicates that cAMP generated in C may migrate to N via gap junctions where it could effect activation of cAMP-PK. These results also indicated that the mammalian lens contains all the components necessary for signal transduction by cAMP.