Synergetic Effect of Recoverin and Calmodulin on Regulation of Rhodopsin Kinase

Abstract

Phosphorylation of photoactivated rhodopsin by rhodopsin kinase (RK or GRK1), a first step of the phototransduction cascade turnoff, is under the control of Ca2+/recoverin. Here, we demonstrate that calmodulin, a ubiquitous Ca2+-sensor, can inhibit RK, though less effectively than recoverin does. We have utilized the surface plasmon resonance technology to map the calmodulin binding site in the RK molecule. Calmodulin does not interact with the recoverin-binding site within amino acid residues M1-S25 of the enzyme. Instead, the high affinity calmodulin binding site is localized within a stretch of amino acid residues V150-K175 in the N-terminal regulatory region of RK. Moreover, the inhibitory effect of calmodulin and recoverin on RK activity is synergetic, which is in agreement with the existence of separate binding sites for each Ca2+-sensing protein. The synergetic inhibition of RK by both Ca2+-sensors occurs over a broader range of Ca2+-concentration than by recoverin alone, indicating increased Ca2+-sensitivity of RK regulation in the presence of both Ca2+-sensors. Taken together, our data suggest that RK regulation by calmodulin in photoreceptor cells could complement the well-known inhibitory effect of recoverin on RK.

Transcriptional analysis of rat photoreceptor cells reveals daily regulation of genes important for visual signaling and light damage susceptibility

“…; Grigoriev et al . ) is consistent with a key role of Grk1 in regulating the daily adjustment of visual processing and sensitivity (for review, see Barlow ). Furthermore, Grk1 deficiency causes light‐dependent retinal degeneration (Chen et al .…”

Ca²⁺-Myristoyl Switch in Neuronal Calcium Sensor-1: A Role of C-Terminal Segment

“…The extraction was performed on ice for 1 h and followed by centrifugation at 27000 g. Both supernatants were mixed and adjusted to 3 mM CaCl 2 . ROS extract was obtained similarly from isolated ROS, prepared from frozen bovine retinas as described previously [55].…”

A Calcium-Relay Mechanism in Vertebrate Phototransduction

“…74 A more recent biochemical study also showed that the Ca 2+ -sensitive inhibition of rhodopsin kinase by recoverin can be increased by the synergetic effect of calmodulin placing the inhibitory action in a range of 0.05−1 μM free Ca 2+ -concentration. 75 This mechanism of shifting the Ca 2+ -sensitive regulation of the target enzyme rhodopsin kinase is reminiscent of the Ca 2+ -relay model described above for the GCAPs and its physiological relevance is an open question for future studies.…”