Abstract
Purpose::
To determine the subcellular localization of prominin-1 in X. laevis photoreceptors and to investigate its role in disk morphogenesis.
Methods::
Double immunostaining was performed to label cryosections of eyes of X. laevis tadpoles, using polyclonal antibodies prepared against either N- or C-terminal of X. laevis prominin-1 (xProm-1) and monoclonal antibody Xper5A11 (a gift from Dr. Robert Molday, University of British Columbia, Vancouver, B.C., Canada) against the C-terminal of peripherin-2/rds. Confocal images were obtained using a Zeiss 510 LSM at the Center for Cell Analysis and Modeling, UCHC.
Results::
Both anti-xProm-1 N- and C-terminal polyclonal antibodies asymmetrically label the rims of the cone outer segments. Double immunolabeling of cones reveals that xProm-1 is localized in the cone lamellar rim opposite to the axoneme of the cone outer segment, while peripherin-2/rds is localized to the opposite lamellar rims on the same side as the axoneme. The site of the axoneme was identified with anti-tubulin antibodies. Both anti-xProm-1 N- and C-terminal polyclonal antibodies also label the base of the rod outer segment as a thin band, while anti-peripherin-2/rds labels the rims and insisures of mature rod outer segment disks. There is no detectable overlap of the immunolabeling of prominin-1 and peripherin-2/rds.
Conclusions::
Prominin-1 and peripherin-2/rds reside in mutually exclusive membrane domains of cone and rod outer segment membranes in X. laevis retinas: Prominin-1 seems to be specifically associated with the open lamellae, whereas peripherin-2/rds specially associated with the rim of the closed disk rims near the ciliary axoneme. This observation indicates that prominin-1 may function as an anti-fusogenic factor and conteract the action of peripherin-2/rds in the process of disk closure and separation from the outer segment plasma membrane.
Keywords: photoreceptors • retina • metabolism