In the pineal gland, the membrane guanylate cyclase activity was specifically stimulated by α(2D/A)-adrenergic receptor (α(2D/A)-AR) agonists. The agonists, however, did not stimulate the cyclase activity in the cell-free membranes. It was possible to stimulate the cyclase in cell-free membranes by the addition of the pineal soluble fraction, but this stimulation was Ca2+ dependent and α(2D/A)-agonist-independent. It was also possible to achieve Ca2+-dependent stimulation of the cyclase by the direct addition of CD-GCAP to the isolated pineal membranes. GD-GCAP is a Ca2+-binding protein and is a specific activator of one of the two membranes of the ROS-GC subfamily of membrane guanylate cyclases, ROS-GC1. The soluble fraction of the pineal gland stimulated recombinant ROS-GC1 in a Ca2+ dependent fashion. The direct presence of both ROS-GC1 and CD-GCAP in the pineal was established by molecular cloning/PCR studies. The findings demonstrate the existence of a novel signal transduction mechanism - the linkage of the α(2D/A)-AR signaling system with ROS-GC1 transduction system, occurring through intracellular Ca2+ via CD-GCAP.
All Science Journal Classification (ASJC) codes
- Structural Biology
- Molecular Biology
- Cell Biology