Novel role for a complement regulatory protein (CD46) in retinal pigment epithelial adhesion.
OBJECTIVE
There is increasing evidence that the complement system may play a significant role in one of the leading diseases causing blindness in the elderly population, age-related macular degeneration. In this study, a novel role in the retina for a regulatory protein in the complement system, CD46, is proposed.


METHODS
The retinal pigment epithelium (RPE) was obtained from human donor eyes as well as human immortalized RPE cell lines (ARPE19). Immunohistochemistry and confocal microscopy were used to immunolocalize CD46 and beta1 integrin. Immunoprecipitation experiments with antibodies to either CD46 or beta1 integrin were performed on RPE cell lysates. A cell adhesion assay was used to determine the proportion of RPE cells that adhere to Bruch's membrane explants from donor eyes.


RESULTS
Immunohistochemistry and confocal microscopy demonstrated that CD46 was polarized to the basal surface of the RPE along with beta1 integrin, shown previously to be involved in RPE adhesion. Immunoprecipitation experiments demonstrated that CD46 and beta1 integrin coprecipitated from RPE cell lysates when either protein was used as the precipitating antibody. The adhesion assay showed that antibodies to either CD46 or beta1 integrin reduced RPE adhesion to the surface of Bruch's membrane compared with the control.


CONCLUSIONS
These findings suggest that this complement regulatory protein, which protects host cells from autologous complement attack, may have a functional interaction with beta1 integrin in the eye that is related to RPE adhesion to its basement membrane and Bruch's membrane.
McLaughlin
Barbara J
BJ
Department of Ophthalmology and Visual Sciences, University of Louisville School of Medicine, Louisville, Kentucky, USA. bjmcla01@gwise.louisville.edu
Fan
Wei
W
Zheng
Jing Juan
JJ
Cai
Hui
H
Del Priore
Lucian V
LV
Bora
Nalini S
NS
Kaplan
Henry J
HJ
D000368:Aged; D015703:Antigens, CD / Q000502:physiology*; D016570:Bruch Membrane / Q000378:metabolism*; D002448:Cell Adhesion / Q000502:physiology; D002460:Cell Line; D003169:Complement Inactivator Proteins / Q000502:physiology*; D006801:Humans; D015151:Immunoblotting; D007124:Immunoenzyme Techniques; D019012:Integrin beta1 / Q000378:metabolism; D051916:Membrane Cofactor Protein; D008562:Membrane Glycoproteins / Q000502:physiology*; D018613:Microscopy, Confocal; D008875:Middle Aged; D010857:Pigment Epithelium of Eye / Q000166:cytology / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D015703:Antigens, CD; C497857:CD46 protein, human; D003169:Complement Inactivator Proteins; D019012:Integrin beta1; D051916:Membrane Cofactor Protein; D008562:Membrane Glycoproteins