Overexpression of rhodopsin alters the structure and photoresponse of rod photoreceptors.

Wen XH, Shen L, Brush RS, Michaud N, Al-Ubaidi MR, Gurevich VV, Hamm HE, Lem J, Dibenedetto E, Anderson RE, Makino CL
Biophys J. 2009 96 (3): 939-50

PMID: 19186132 · PMCID: PMC2716671 · DOI:10.1016/j.bpj.2008.10.016

Rhodopsins are densely packed in rod outer-segment membranes to maximize photon absorption, but this arrangement interferes with transducin activation by restricting the mobility of both proteins. We attempted to explore this phenomenon in transgenic mice that overexpressed rhodopsin in their rods. Photon capture was improved, and, for a given number of photoisomerizations, bright-flash responses rose more gradually with a reduction in amplification--but not because rhodopsins were more tightly packed in the membrane. Instead, rods increased their outer-segment diameters, accommodating the extra rhodopsins without changing the rhodopsin packing density. Because the expression of other phototransduction proteins did not increase, transducin and its effector phosphodiesterase were distributed over a larger surface area. That feature, as well as an increase in cytosolic volume, was responsible for delaying the onset of the photoresponse and for attenuating its amplification.

MeSH Terms (12)

Absorption Animals Cattle Cell Membrane Fatty Acids Gene Expression Light Mice Mice, Transgenic Retinal Rod Photoreceptor Cells Rhodopsin Rod Opsins

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