The expression of L-type voltage-gated calcium channels in retinal photoreceptors is under circadian control.
Photoreceptors are non-spiking neurons, and their synapses mediate the continuous release of neurotransmitters under the control of L-type voltage-gated calcium channels (VGCCs). Photoreceptors express endogenous circadian oscillators that play important roles in regulating photoreceptor physiology and function. Here, we report that the L-type VGCCs in chick cone photoreceptors are under circadian control. The L-type VGCC currents are greater when measured during the subjective night than during the subjective day. Using antibodies against the VGCCalpha1C and VGCCalpha1D subunits, we found that the immunofluorescence intensities of both VGCCalpha1C and VGCCalpha1D in photoreceptors are higher during the subjective night. However, the mRNA levels of VGCCalpha1D, but not VGCCalpha1C, are rhythmic. Nocturnal increases in L-type VGCCs are blocked by manumycin A, PD98059, and KN93, which suggest that the circadian output pathway includes Ras, Erk, and calcium-calmodulin dependent kinase II. In summary, four independent lines of evidence show that the L-VGCCs in cone photoreceptors are under circadian control.
Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas 77843, USA.
Michael L
ML
Ko
Yilin
Y
Liu
Stuart E
SE
Dryer
Gladys Y-P
GY
Ko
D000818:Animals; D015153:Blotting, Western; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000096:biosynthesis* / Q000235:genetics; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000502:physiology; D002478:Cells, Cultured; D002642:Chick Embryo; D002940:Circadian Rhythm / Q000502:physiology*; D005455:Fluorescent Antibody Technique; D011905:Genes, ras / Q000502:physiology; D007150:Immunohistochemistry; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology; D018408:Patch-Clamp Techniques; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis; D012160:Retina / Q000378:metabolism / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D012333:RNA, Messenger; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D020928:Mitogen-Activated Protein Kinases