Mg²⁺‐ATP induces filament growth from retinal rod outer segments with disrupted plasma membranes

Abstract

MgZ+-ATP produces a large decrease in near-IR light scattering when added to suspensions of rod outer segments (ROS) when the plasma membranes have been disrupted by a gentle dialysis procedure. When this process is studied by light microscopy with video-enhanced image contrast, the Mg2+-ATP-dependent signal is seen to be associated with the formation of filaments which extend only from those ROS lacking plasma membranes. Both the IR light scattering signal and filament growth are inhibited by vanadate and DCCD but not by colchicine, colcemid or cytochalasins.

cGMP phosphodiesterase dependent light-induced scattering changes in suspensions of retinal disk membranes

“…swelling was also described by Uhl et al (1979), Parker et al (1987) report an ATP-dependent light-scattering change associated with filament formation. Their ATP and membrane concentration dependence is, however, very different from that in our experiments: half-saturation at 400 /uM ATP (compared to about 100 /nM) and optimal effect for 100 /uM rhodopsin (while all our experiments are carried out at 2-10 /nM rhodopsin); the existence of a relation between their G+ signal [described by Lewis et al (1984), apparently identical to the PAS] and their ATP-dependent filament formation is not observed, the amplitude of the G+ signal being on the contrary smaller in preparations which show better filament growth.…”

Recent Chemical Studies Related to Vision

“…Advanced ultrastructural and ultraimmunohistochemical studies provide increasing evidence that an elaborate cytoskeletal network stabilizes the rod outer segment (Usukura and Yamada, 1981;Roof and Heuser, 1982;Wong and Molday, 1986;Parker et al, 1987;Corless et al, 1987a) as well as the rhabdomere (Saibil and Hewat, 1987). In addition, the characteristic disk-like structure of the vertebrate photoreceptormembrane might well be stabilized by specific 'rim-proteins' like the 240 kDa protein (Papermaster et al, 1978) and the 33 kDa protein ('peripherin'; Molday et al, 1987).…”