title: Two eye guanylyl cyclases are expressed in the same photoreceptor cells and form homomers in preference to heteromers.
abstract: We recently described two eye guanylyl cyclases (GC-E and GC-F) that contain an apparent extracellular domain potentially capable of binding ligands (Yang, R.-B., Foster, D. C., Garbers, D. L., and Fülle, H.-J. (1995) Proc. Natl. Acad. Sci. U. S. A. 92, 602-606). Here, Northern and Western analyses showed that both cyclases are expressed in the retina and enriched in photoreceptor outer segments. By the use of specific GC-E and GC-F antibodies coupled to different sized gold particles both cyclases were colocalized within the same photoreceptor cells raising the possibility of homomeric and/or heteromeric interactions. A point mutant of GC-E (D878A) was constructed and expressed; it contained no detectable cyclase activity but acted in a dominant negative fashion to abolish the activity of native GC-E and GC-F in coexpression studies. These results suggested that GC-E and GC-F could form either homomers or heteromers, at least when overexpressed in COS-7 cells. Immunoprecipitation with GC-E and GC-F antibody followed by Western analysis confirmed that both homomers and heteromers could be formed. However, similar experiments using retina or outer segments revealed that a vast majority of GC-E and GC-F were precipitated as homomers in the eye. Therefore, like other members of the membrane guanylyl cyclase subfamily, GC-E and GC-F appear to preferentially form homomers.
authors.affiliation: Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75235-9050, USA.
authors.forename: R B
authors.initials: RB
authors.lastname: Yang
authors.forename: D L
authors.initials: DL
authors.lastname: Garbers
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D019556:COS Cells; D005260:Female; D006162:Guanylate Cyclase / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D008970:Molecular Weight; D010786:Photoreceptor Cells / Q000201:enzymology*; D017354:Point Mutation; D011487:Protein Conformation; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011956:Receptors, Cell Surface; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled; D018000:Receptors, Peptide / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D012374:Rod Cell Outer Segment / Q000201:enzymology; D012995:Solubility
chemical_list: D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D018000:Receptors, Peptide; D011994:Recombinant Proteins; D006162:Guanylate Cyclase; C484781:Gucy2e protein, rat; C484785:Gucy2f protein, rat; D000074261:Receptors, Enterotoxin; D050705:Receptors, Guanylate Cyclase-Coupled