TY - JOUR
T1 - Elementary response triggered by transducin in retinal rods
AU - Yue, Wendy W.S.
AU - Silverman, Daniel
AU - Ren, Xiaozhi
AU - Frederiksen, Rikard
AU - Sakai, Kazumi
AU - Yamashita, Takahiro
AU - Shichida, Yoshinori
AU - Cornwall, M. Carter
AU - Chen, Jeannie
AU - Yau, King Wai
N1 - Funding Information:
ACKNOWLEDGMENTS. We thank Drs. Ching-Kang Jason Chen (Baylor College of Medicine) and Janis Lem (Tufts University) for the Grk1S561L and Gnat1−/− mouse lines, respectively; Drs. Robert S. Molday (University of British Columbia), Alexander M. Dizhoor (Salus University), Ching-Kang Jason Chen (Baylor College of Medicine), and Theodore G. Wensel (Baylor College of Medicine) for antibodies; and Drs. Marie E. Burns and Edward N. Pugh, Jr. (University of California, Davis), Trevor D. Lamb (Australian National University), Jeremy Nathans and Randall Reed (Johns Hopkins University), David Julius and Nicholas Bellono (University of California, San Francisco), Donggen Luo (Peking University), and members of the K.-W.Y. laboratory for discussions. This work was supported by National Institutes of Health Grants EY006837 (to K.-W.Y.), EY001157 (to M.C.C.), and EY012155 (to J.C.); the António Champalimaud Vision Award, Portugal (to K.-W.Y.); a Howard Hughes Medical Institute International Predoctoral Fellowship (to W.W.S.Y.); and Visual Science Training Program Fellowship EY007143 from the National Eye Institute (to D.S.).
Publisher Copyright:
© 2019 National Academy of Sciences. All Rights Reserved.
PY - 2019
Y1 - 2019
N2 - G protein-coupled receptor (GPCR) signaling is crucial for many physiological processes. A signature of such pathways is high amplification, a concept originating from retinal rod phototransduction, whereby one photoactivated rhodopsin molecule (Rho ∗ ) was long reported to activate several hundred transducins (G T ∗ s), each then activating a cGMP-phosphodiesterase catalytic subunit (G T ∗ ·PDE ∗ ). This high gain at the Rho ∗ -to-G T ∗ step has been challenged more recently, but estimates remain dispersed and rely on some nonintact rod measurements. With two independent approaches, one with an extremely inefficient mutant rhodopsin and the other with WT bleached rhodopsin, which has exceedingly weak constitutive activity in darkness, we obtained an estimate for the electrical effect from a single G T ∗ ·PDE ∗ molecular complex in intact mouse rods. Comparing the single-G T ∗ ·PDE ∗ effect to the WT single-photon response, both in Gcaps -/- background, gives an effective gain of only ~12-14 G T ∗ ·PDE ∗ s produced per Rho ∗ . Our findings have finally dispelled the entrenched concept of very high gain at the receptor-to-G protein/effector step in GPCR systems.
AB - G protein-coupled receptor (GPCR) signaling is crucial for many physiological processes. A signature of such pathways is high amplification, a concept originating from retinal rod phototransduction, whereby one photoactivated rhodopsin molecule (Rho ∗ ) was long reported to activate several hundred transducins (G T ∗ s), each then activating a cGMP-phosphodiesterase catalytic subunit (G T ∗ ·PDE ∗ ). This high gain at the Rho ∗ -to-G T ∗ step has been challenged more recently, but estimates remain dispersed and rely on some nonintact rod measurements. With two independent approaches, one with an extremely inefficient mutant rhodopsin and the other with WT bleached rhodopsin, which has exceedingly weak constitutive activity in darkness, we obtained an estimate for the electrical effect from a single G T ∗ ·PDE ∗ molecular complex in intact mouse rods. Comparing the single-G T ∗ ·PDE ∗ effect to the WT single-photon response, both in Gcaps -/- background, gives an effective gain of only ~12-14 G T ∗ ·PDE ∗ s produced per Rho ∗ . Our findings have finally dispelled the entrenched concept of very high gain at the receptor-to-G protein/effector step in GPCR systems.
KW - Apo-opsin
KW - G protein-coupled receptor
KW - Rhodopsin
KW - Rod phototransduction
KW - Signal amplification
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U2 - 10.1073/pnas.1817781116
DO - 10.1073/pnas.1817781116
M3 - Article
C2 - 30796193
AN - SCOPUS:85062866293
VL - 116
SP - 5144
EP - 5153
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
SN - 0027-8424
IS - 11
ER -