title: Guanylate cyclase-G, expressed in the Grueneberg ganglion olfactory subsystem, is activated by bicarbonate.
abstract: GC (guanylate cyclase)-G is the most recently identified member of the receptor GC family. However, the regulation of its activity and protein expression in the mammalian olfactory system remains unclear. In the present study, we used a GC-G-specific antibody to validate that the GC-G protein is expressed in Grueneberg ganglion neurons, a newly recognized olfactory subsystem co-expressing other cGMP signalling components such as the cGMP-regulated PDE2A (phosphodiesterase 2A) and the cGMP-gated ion channel CNGA3 (cyclic nucleotide-gated cation channel α-3). Further molecular and biochemical analyses showed that heterologously expressed GC-G protein, specifically the C-terminal cyclase domain, was directly stimulated by bicarbonate in both in vivo cellular cGMP accumulation assays in human embryonic kidney-293T cells and in vitro GC assays with a purified recombinant protein containing the GC domain. In addition, overexpression of GC-G in NG108 neuronal cells resulted in a CO2-dependent increase in cellular cGMP level that could be blocked by treatment with acetazolamide, an inhibitor of carbonic anhydrases, which implies that the stimulatory effect of CO2 requires its conversion to bicarbonate. Together, our data demonstrate a novel CO2/bicarbonate-dependent activation mechanism for GC-G and suggest that GC-G may be involved in a wide variety of CO2/bicarbonate-regulated biological processes such as the chemosensory function in Grueneberg ganglion neurons.
authors.affiliation: Molecular Medicine Program, Taiwan International Graduate Program, Academia Sinica, Taipei 115, Taiwan.
authors.forename: Ying-Chi
authors.initials: YC
authors.lastname: Chao
authors.forename: Chien-Jui
authors.initials: CJ
authors.lastname: Cheng
authors.forename: Hsiu-Ting
authors.initials: HT
authors.lastname: Hsieh
authors.forename: Chih-Ching
authors.initials: CC
authors.lastname: Lin
authors.forename: Chien-Chang
authors.initials: CC
authors.lastname: Chen
authors.forename: Ruey-Bing
authors.initials: RB
authors.lastname: Yang
mesh_terms: D000818:Animals; D000918:Antibody Specificity; D001639:Bicarbonates / Q000494:pharmacology; D020134:Catalytic Domain; D002460:Cell Line; D004926:Escherichia coli / Q000235:genetics; D005982:Glutathione Transferase / Q000235:genetics; D006162:Guanylate Cyclase / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000201:enzymology; D009833:Olfactory Pathways / Q000166:cytology / Q000201:enzymology*; D010957:Plasmids; D011993:Recombinant Fusion Proteins / Q000235:genetics
chemical_list: D001639:Bicarbonates; D011993:Recombinant Fusion Proteins; D005982:Glutathione Transferase; D006162:Guanylate Cyclase