Differential activation of rod outer segment membrane guanylate cyclases, ROS-GC1 and ROS-GC2, by CD-GCAP and identification of the signaling domain.
The ROS-GC is one of the two subfamilies of membrane guanylate cyclases. It distinguishes itself from the other surface receptor subfamily in that its members are not regulated by extracellular peptides; instead, they are modulated by intracellular Ca2+ signals. There are two members of the subfamily, ROS-GC1 and ROS-GC2. An intriguing feature of ROS-GC1 is that it has two Ca2+ switches. One switch inhibits the enzyme at micromolar concentrations of Ca2+, and the other stimulates. The inhibitory switch is linked to phototransduction, and it is likely that the stimulatory switch is linked to retinal synaptic activity. Ca2+ acts indirectly via Ca(2+)-binding proteins, GCAPs and CD-GCAP. GCAPs modulate the inhibitory switching component of the cyclase and CD-GCAP turns on the activation signaling switch. The activating switch of ROS-GC2 has not so far been scrutinized. The present study shows that CD-GCAP is linked to the activation signaling switch of ROS-GC2, but the linkage is about 10-fold weaker than that of the ROS-GC1. Thus, CD-GCAP is a specific ROS-GC1 activator. Furthermore, through a series of expression studies on the mutants involving deletion, building of hybrids, and reconstruction of a heterologous cyclase, the study confirms that the CD-GCAP regulated switch resides within the amino acid segment 736-1053 of the cyclase.
Duda
T
T
Department of Cell Biology, University of Medicine and Dentistry of New Jersey, Stratford 08084, USA.
Goraczniak
R M
RM
Pozdnyakov
N
N
Sitaramayya
A
A
Sharma
R K
RK
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002417:Cattle; D004789:Enzyme Activation; D006162:Guanylate Cyclase / Q000235:genetics / Q000378:metabolism*; D051604:Guanylate Cyclase-Activating Proteins; D009154:Mutation; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012374:Rod Cell Outer Segment / Q000201:enzymology*; D017384:Sequence Deletion; D014785:Vision, Ocular
D002135:Calcium-Binding Proteins; D051604:Guanylate Cyclase-Activating Proteins; D011993:Recombinant Fusion Proteins; D006162:Guanylate Cyclase; D002118:Calcium