In vivo optophysiology reveals that G-protein activation triggers osmotic swelling and increased light scattering of rod photoreceptors

Pengfei Zhang, Robert Zawadzki, Mayank Goswami, Phuong T. Nguyen, Vladimir Yarov-Yarovoy, Marie E Burns, Edward N Pugh Jr

Research output: Contribution to journalArticle

34 Scopus citations

Abstract

The light responses of rod and cone photoreceptors have been studied electrophysiologically for decades, largely with ex vivo approaches that disrupt the photoreceptors' subretinal microenvironment. Here we report the use of optical coherence tomography (OCT) to measure light-driven signals of rod photoreceptors in vivo. Visible light stimulation over a 200-fold intensity range caused correlated rod outer segment (OS) elongation and increased light scattering in wildtype mice, but not in mice lacking the rod G-protein alpha subunit, transducin (Gαt ), revealing these responses to be triggered by phototransduction. For stimuli that photoactivated one rhodopsin per Gαt the rod OS swelling response reached a saturated elongation of 10.0 ± 2.1%, at a maximum rate of 0.11% s-1 . Analyzing swelling as osmotically driven water influx, we find the H2 O membrane permeabilityoftherodOStobe(2.6± 0.4) × 10-5 cm•s-1 , comparable to that of other cells lacking aquaporin expression. Application of Van't Hoff's law reveals that complete activation of phototransduction generates a potentially harmful 20% increase in OS osmotic pressure. The increased backscattering from the base of the OS is explained by a model combining cytoplasmic swelling, translocation of dissociated G-protein subunits from the disc membranes into the cytoplasm, and a relatively higher H2 O permeability of nascent discs in the basal rod OS. Translocation of phototransduction components out of the OS may protect rods from osmotic stress, which could be especially harmful in disease conditions that affect rod OS structural integrity.

Original languageEnglish (US)
Pages (from-to)E2937-E2946
JournalProceedings of the National Academy of Sciences of the United States of America
Volume114
Issue number14
DOIs
StatePublished - Apr 4 2017

Keywords

  • Intrinsic optical signals
  • Optical coherence tomography
  • Osmotic stress
  • Photoreceptor waveguiding
  • Phototransduction

ASJC Scopus subject areas

  • General

Fingerprint Dive into the research topics of 'In vivo optophysiology reveals that G-protein activation triggers osmotic swelling and increased light scattering of rod photoreceptors'. Together they form a unique fingerprint.

  • Cite this