Third calcium-modulated rod outer segment membrane guanylate cyclase transduction mechanism

被引:45
作者
Krishnan, A
Goraczniak, RM
Duda, T
Sharma, RK [1 ]
机构
[1] Univ Med & Dent New Jersey, Dept Cell Biol, Unit Regulatory & Mol Biol, Stratford, NJ 08084 USA
[2] Univ Med & Dent New Jersey, Dept Ophthalmol NJMS, Stratford, NJ 08084 USA
关键词
guanylate cyclase; rod outer segment; activating protein; phototransduction; calcium modulation;
D O I
10.1023/A:1006860018300
中图分类号
Q2 [细胞生物学];
学科分类号
071009 ; 090102 ;
摘要
Ca2+-modulated rod outer segment membrane guanylate cyclase (ROS-GC1) has been cloned and reconstituted to show that it is regulated by two processes: one inhibitory, the other stimulatory. The inhibitory process is consistent with its linkage to phototransduction; the physiology of the stimulatory process is probably linked to neuronal transmission. In both regulatory processes, calcium modulation of the cyclase takes place through the calcium binding proteins; guanylate cyclase activating proteins (GCAP1 and GCAP2) in the case of the phototransduction process and calcium-dependent GCAP (CD-GCAP) in the case of the stimulatory process. The cyclase domains involved in the two processes are located at two different sites on the ROS-GC1 intracellular region. The GCAP1-modulated domain resides within the aa 447-730 segment of ROS-GC1 and the CD-GCAP-modulated domain resides within the aa 731-1054 segment. In the present study the GCAP2-dependent Ca2+ modulation of the cyclase activity has been reconstituted using recombinant forms of GCAP2 and ROS-GC1, and its mutants. The results indicate that consistent to phototransduction, GCAP2 at low Ca2+ concentration(10 nM) maximally stimulates the cyclase activity of the wild-type and its mutants: ext(-) (deleted aa 8-408); kin(-) (deleted aa 447-730) and hybrid consisting of the ext, transmembrane and kin domains of ANF-RGC and the C-terminal domain, aa 731-1054, of ROS-GC1. In all cases, it inhibits the cyclase activity with an IC50 of about 140 nM. A previous study has shown that under identical conditions the kin(-) and the hybrid mutant are at best only minimally stimulated. Thus, the GCAP1 and GCAP2 signal transduction mechanisms are different, occurring through different modules of ROS-GC1. These findings also demonstrate that the intracellular region of ROS-GC1 is composed of multiple modules, each designed to mediate a particular calcium-specific signalling pathway.
引用
收藏
页码:251 / 259
页数:9
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