Photoreceptor disc membranes are formed through an Arp2/3-dependent lamellipodium-like mechanism.

Journal Article (Journal Article)

The light-sensitive outer segment of the vertebrate photoreceptor is a highly modified primary cilium filled with disc-shaped membranes that provide a vast surface for efficient photon capture. The formation of each disc is initiated by a ciliary membrane evagination driven by an unknown molecular mechanism reportedly requiring actin polymerization. Since a distinct F-actin network resides precisely at the site of disc morphogenesis, we employed a unique proteomic approach to identify components of this network potentially driving disc morphogenesis. The only identified actin nucleator was the Arp2/3 complex, which induces the polymerization of branched actin networks. To investigate the potential involvement of Arp2/3 in the formation of new discs, we generated a conditional knockout mouse lacking its essential ArpC3 subunit in rod photoreceptors. This knockout resulted in the complete loss of the F-actin network specifically at the site of disc morphogenesis, with the time course of ArpC3 depletion correlating with the time course of F-actin loss. Without the actin network at this site, the initiation of new disc formation is completely halted, forcing all newly synthesized membrane material to be delivered to the several nascent discs whose morphogenesis had already been in progress. As a result, these discs undergo uncontrolled expansion instead of normal enclosure, which leads to formation of unusual, large membrane whorls. These data suggest a model of photoreceptor disc morphogenesis in which Arp2/3 initiates disc formation in a "lamellipodium-like" mechanism.

Full Text

Duke Authors

Cited Authors

  • Spencer, WJ; Lewis, TR; Phan, S; Cady, MA; Serebrovskaya, EO; Schneider, NF; Kim, K-Y; Cameron, LA; Skiba, NP; Ellisman, MH; Arshavsky, VY

Published Date

  • December 16, 2019

Published In

PubMed ID

  • 31843915

Pubmed Central ID

  • PMC6936530

Electronic International Standard Serial Number (EISSN)

  • 1091-6490

Digital Object Identifier (DOI)

  • 10.1073/pnas.1913518117

Language

  • eng

Conference Location

  • United States