Effects of low AIPL1 expression on phototransduction in rods.
OBJECTIVE
To investigate the impact of aryl hydrocarbon receptor-interacting protein-like (AIPL)-1 on photoreception in rods.


METHODS
Photoresponses of mouse rods expressing lowered amounts of AIPL1 were studied by single-cell and electroretinogram (ERG) recordings. Phototransduction protein levels and enzymatic activities were determined in biochemical assays. Ca2+ dynamics were probed with a fluorescent dye. Comparisons were made to rods expressing mutant Y99C guanylate cyclase activating protein (GCAP)-1, to understand which effects arose from elevated dark levels of cGMP and Ca2+.


RESULTS
Except for PDE, transduction protein levels were normal in low-AIPL1 retinas, as were guanylate cyclase (GC), rhodopsin kinase (RK), and normalized phosphodiesterase (PDE) activities. Y99C and low-AIPL1 rods were more sensitive to flashes than normal, but flash responses of low-AIPL1 rods showed an abnormal delay, reduced rate of increase, and longer recovery not present in Y99C rod responses. In addition, low-AIPL1 rods but not Y99C rods failed to reach the normal light-induced minimum in Ca2+ concentration.


CONCLUSIONS
Reduced AIPL1 delayed the photoresponse, decreased its amplification constant, slowed a rate-limiting step in its recovery, and limited the light-induced decrease in Ca2+. Not all changes were attributable to decreased PDE or to elevated cGMP and Ca2+ in darkness. Therefore, AIPL1 directly or indirectly affects more than one component of phototransduction.
Makino
Clint L
CL
Howe Laboratory, Department of Ophthalmology, Massachusetts Eye and Ear Infirmary and Harvard Medical School, Boston 02114, USA. cmakino@meei.harvard.edu
Wen
Xiao-Hong
XH
Michaud
Norman
N
Peshenko
Igor V
IV
Pawlyk
Basil
B
Brush
Richard S
RS
Soloviev
Maria
M
Liu
Xiaoqing
X
Woodruff
Michael L
ML
Calvert
Peter D
PD
Savchenko
Andrey B
AB
Anderson
Robert E
RE
Fain
Gordon L
GL
Li
Tiansen
T
Sandberg
Michael A
MA
Dizhoor
Alexander M
AM
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002352:Carrier Proteins / Q000502:physiology*; D002849:Chromatography, Gas; D006152:Cyclic GMP / Q000378:metabolism; D004596:Electroretinography; D005227:Fatty Acids / Q000378:metabolism; D051606:G-Protein-Coupled Receptor Kinase 1 / Q000378:metabolism; D006162:Guanylate Cyclase / Q000378:metabolism; D051604:Guanylate Cyclase-Activating Proteins / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D010775:Photic Stimulation; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology* / Q000528:radiation effects; D015293:Transducin / Q000378:metabolism; D014785:Vision, Ocular / Q000502:physiology*
D048868:Adaptor Proteins, Signal Transducing; C498604:Aipl1 protein, mouse; D002352:Carrier Proteins; D005227:Fatty Acids; D051604:Guanylate Cyclase-Activating Proteins; C496737:Guca1a protein, mouse; D051606:G-Protein-Coupled Receptor Kinase 1; D010727:Phosphoric Diester Hydrolases; D015293:Transducin; D006162:Guanylate Cyclase; D006152:Cyclic GMP; D002118:Calcium