Calcium-modulated membrane guanylate cyclase in synaptic transmission?
Rod outer segment guanylate cyclase 1 (ROS-GC1) is a pivotal enzyme for vertebrate phototransduction and the systematically growing evidence point to its connection with processes other than phototransduction within and outside the retina. ROS-GC1 activity is regulated by Ca2+ in two opposite modes. This regulation is indirect and occurs through Ca+-binding proteins. At nanomolar Ca2+ concentrations, ROS-GC1 is activated by GCAPs and at micromolar Ca2+-concentrations, by S100beta and neurocalcin. The former mode operates in phototransduction and the latter was proposed to play a role in synaptic activity. The last possibility was supported by findings of ROS-GC1 expression not only in various retinal layers other than photoreceptor outer segments but also outside the retina, in pineal gland and olfactory bulb. If ROS-GC1 indeed is to play a role in neurotransmission its expression must be colocalized with its Ca2+-dependent regulators and with possible targets of an increased cyclic GMP concentration, cyclic nucleotide-gated channels or cyclic GMP-dependent protein kinase, in synaptic regions. In this review these aspects of ROS-GC1 expression in retina, pineal gland and olfactory bulb are discussed.
Duda
Teresa
T
Department of Cell Biology, SOM and NJMS University of Medicine and Dentistry of New Jersey, Stratford 08084, USA. dudatm@umdnj.edu
Koch
Karl-Wilhelm
KW
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology* / Q000378:metabolism; D006162:Guanylate Cyclase / Q000378:metabolism*; D006801:Humans; D009830:Olfactory Bulb / Q000201:enzymology; D009928:Organ Specificity; D012160:Retina / Q000166:cytology / Q000201:enzymology / Q000378:metabolism; D012374:Rod Cell Outer Segment / Q000201:enzymology; D013569:Synapses / Q000201:enzymology* / Q000378:metabolism; D009435:Synaptic Transmission
D006162:Guanylate Cyclase; D002118:Calcium