Cloning and expression of a second photoreceptor-specific membrane retina guanylyl cyclase (RetGC), RetGC-2.
One of the membrane guanylyl cyclases (GCs), RetGC, is expressed predominantly in photoreceptors. No extracellular ligand has been described for RetGC, but it is sensitive to activation by a soluble 24-kDa protein (p24) and is inhibited by Ca2+. This enzyme is, therefore, thought to play a role in resynthesizing cGMP for photoreceptor recovery or adaptation. By screening a human retinal cDNA library at low stringency with the cytoplasmic domains from four cyclases, we cloned cDNAs encoding a membrane CG that is most closely related to RetGC. We have named this GC RetGC-2, and now term the initially described RetGC RetGC-1. By in situ hybridization, mRNA encoding RetGC-2 is found only in the outer nuclear layer and inner segments of photoreceptor cells. By using synthetic peptide antiserum specific for each RetGC subtype, RetGC-2 can be distinguished from RetGC-1 as a slightly smaller protein in immunoblots of bovine rod outer segments. Membrane GC activity of recombinant RetGC-2 expressed in human embryonic kidney 293 cells is stimulated by the activator p24 and is inhibited by Ca2+ with an EC50 value of 50-100 nM. Our data reveal a previously unappreciated diversity of photoreceptor GCs.
Lowe
D G
DG
Genentech, Inc. South San Francisco, CA 94080, USA.
Dizhoor
A M
AM
Liu
K
K
Gu
Q
Q
Spencer
M
M
Laura
R
R
Lu
L
L
Hurley
J B
JB
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology; D003001:Cloning, Molecular; D017931:DNA Primers; D018076:DNA, Complementary; D006162:Guanylate Cyclase / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D017403:In Situ Hybridization; D008253:Macaca mulatta; D008969:Molecular Sequence Data; D010786:Photoreceptor Cells / Q000201:enzymology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D017931:DNA Primers; D018076:DNA, Complementary; D012333:RNA, Messenger; D006162:Guanylate Cyclase