Abstract
Purpose: :
To make a quantitative assessment on the functional presence of the S100B-modulated ROS-GC1 transduction system in the outer segments of photoreceptors, outer (P1) and inner (P2) plexiform layers of the mouse retina.
Methods: :
Biochemical techniques involving guanylate cyclase assays, Western blots and co-immunoprecipitation were used on the membranes of the genetically modified mouse model systems consisting of S100B gene knock-out (k/o), ROS-GC1 k/o, and GCAP1-Y99C.
Results: :
There are four membrane guanylate cyclases in the retina. Two are surface receptors, ANF-RGC and CNP-RGC; and two are Ca2+-modulated, ROS-GC1 and ROS-GC2. The ROS-GC1 percentage presence in the following native compartments of the retina is as follows: outer segments, 95%; P1, 60%; and P2, 50%. The contribution of the S100B-modulation in these native systems is as follows: outer segments, 45%; P1, 30%; and P2, 25%.
Conclusions: :
1) The major phototransduction linked membrane guanylate cyclase is ROS-GC1. ROS-GC2 (4%) has a minor yet significant role. 2) Ca2+-bound S100B modulates the native ROS-GC1 in the three retinal layers--outer segments, P1 and P2. 3) Peptide hormone receptor guanylate cyclases, ANF-RGC and CNP-RGC, have also significant presence in all three retinal layers.
Keywords: calcium • signal transduction • retina: distal (photoreceptors, horizontal cells, bipolar cells)