Rapid kinetics of endocytosis at rod photoreceptor synapses depends upon endocytic load and calcium

Karlene M. Cork, Wallace B Thoreson

Research output: Contribution to journalArticle

4 Citations (Scopus)

Abstract

Release from rods is triggered by the opening of L-type Ca2+ channels that lie beneath synaptic ribbons. After exocytosis, vesicles are retrieved by compensatory endocytosis. Previous work showed that endocytosis is dynamin-dependent in rods but dynamin-independent in cones. We hypothesized that fast endocytosis in rods may also differ from cones in its dependence upon the amount of Ca2+ influx and/or endocytic load. We measured exocytosis and endocytosis from membrane capacitance (C m) changes evoked by depolarizing steps in voltage clamped rods from tiger salamander retinal slices. Similar to cones, the time constant for endocytosis in rods was quite fast, averaging <200 ms. We manipulated Ca2+ influx and the amount of vesicle release by altering the duration and voltage of depolarizing steps. Unlike cones, endocytosis kinetics in rods slowed after increasing Ca2+ channel activation with longer step durations or more strongly depolarized voltage steps. Endocytosis kinetics also slowed as Ca2+ buffering was decreased by replacing BAPTA (10 or 1 mM) with the slower Ca2+ buffer EGTA (5 or 0.5 mM) in the pipette solution. These data provide further evidence that endocytosis mechanisms differ in rods and cones and suggest that endocytosis in rods is regulated by both endocytic load and local Ca 2+ levels.

Original languageEnglish (US)
Pages (from-to)227-235
Number of pages9
JournalVisual Neuroscience
Volume31
Issue number3
DOIs
StatePublished - May 2014

Fingerprint

Retinal Rod Photoreceptor Cells
Endocytosis
Synapses
Calcium
Dynamins
Exocytosis
Ambystoma
Vertebrate Photoreceptor Cells
Egtazic Acid
Buffers

Keywords

  • Endocytosis
  • Exocytosis
  • Retina
  • Ribbon synapse
  • Rod photoreceptors

ASJC Scopus subject areas

  • Physiology
  • Sensory Systems

Cite this

Rapid kinetics of endocytosis at rod photoreceptor synapses depends upon endocytic load and calcium. / Cork, Karlene M.; Thoreson, Wallace B.

In: Visual Neuroscience, Vol. 31, No. 3, 05.2014, p. 227-235.

Research output: Contribution to journalArticle

@article{bfb81e9d63564d0fa2828e3008c84922,
title = "Rapid kinetics of endocytosis at rod photoreceptor synapses depends upon endocytic load and calcium",
abstract = "Release from rods is triggered by the opening of L-type Ca2+ channels that lie beneath synaptic ribbons. After exocytosis, vesicles are retrieved by compensatory endocytosis. Previous work showed that endocytosis is dynamin-dependent in rods but dynamin-independent in cones. We hypothesized that fast endocytosis in rods may also differ from cones in its dependence upon the amount of Ca2+ influx and/or endocytic load. We measured exocytosis and endocytosis from membrane capacitance (C m) changes evoked by depolarizing steps in voltage clamped rods from tiger salamander retinal slices. Similar to cones, the time constant for endocytosis in rods was quite fast, averaging <200 ms. We manipulated Ca2+ influx and the amount of vesicle release by altering the duration and voltage of depolarizing steps. Unlike cones, endocytosis kinetics in rods slowed after increasing Ca2+ channel activation with longer step durations or more strongly depolarized voltage steps. Endocytosis kinetics also slowed as Ca2+ buffering was decreased by replacing BAPTA (10 or 1 mM) with the slower Ca2+ buffer EGTA (5 or 0.5 mM) in the pipette solution. These data provide further evidence that endocytosis mechanisms differ in rods and cones and suggest that endocytosis in rods is regulated by both endocytic load and local Ca 2+ levels.",
keywords = "Endocytosis, Exocytosis, Retina, Ribbon synapse, Rod photoreceptors",
author = "Cork, {Karlene M.} and Thoreson, {Wallace B}",
year = "2014",
month = "5",
doi = "10.1017/S095252381400011X",
language = "English (US)",
volume = "31",
pages = "227--235",
journal = "Visual Neuroscience",
issn = "0952-5238",
publisher = "Cambridge University Press",
number = "3",

}

TY - JOUR

T1 - Rapid kinetics of endocytosis at rod photoreceptor synapses depends upon endocytic load and calcium

AU - Cork, Karlene M.

AU - Thoreson, Wallace B

PY - 2014/5

Y1 - 2014/5

N2 - Release from rods is triggered by the opening of L-type Ca2+ channels that lie beneath synaptic ribbons. After exocytosis, vesicles are retrieved by compensatory endocytosis. Previous work showed that endocytosis is dynamin-dependent in rods but dynamin-independent in cones. We hypothesized that fast endocytosis in rods may also differ from cones in its dependence upon the amount of Ca2+ influx and/or endocytic load. We measured exocytosis and endocytosis from membrane capacitance (C m) changes evoked by depolarizing steps in voltage clamped rods from tiger salamander retinal slices. Similar to cones, the time constant for endocytosis in rods was quite fast, averaging <200 ms. We manipulated Ca2+ influx and the amount of vesicle release by altering the duration and voltage of depolarizing steps. Unlike cones, endocytosis kinetics in rods slowed after increasing Ca2+ channel activation with longer step durations or more strongly depolarized voltage steps. Endocytosis kinetics also slowed as Ca2+ buffering was decreased by replacing BAPTA (10 or 1 mM) with the slower Ca2+ buffer EGTA (5 or 0.5 mM) in the pipette solution. These data provide further evidence that endocytosis mechanisms differ in rods and cones and suggest that endocytosis in rods is regulated by both endocytic load and local Ca 2+ levels.

AB - Release from rods is triggered by the opening of L-type Ca2+ channels that lie beneath synaptic ribbons. After exocytosis, vesicles are retrieved by compensatory endocytosis. Previous work showed that endocytosis is dynamin-dependent in rods but dynamin-independent in cones. We hypothesized that fast endocytosis in rods may also differ from cones in its dependence upon the amount of Ca2+ influx and/or endocytic load. We measured exocytosis and endocytosis from membrane capacitance (C m) changes evoked by depolarizing steps in voltage clamped rods from tiger salamander retinal slices. Similar to cones, the time constant for endocytosis in rods was quite fast, averaging <200 ms. We manipulated Ca2+ influx and the amount of vesicle release by altering the duration and voltage of depolarizing steps. Unlike cones, endocytosis kinetics in rods slowed after increasing Ca2+ channel activation with longer step durations or more strongly depolarized voltage steps. Endocytosis kinetics also slowed as Ca2+ buffering was decreased by replacing BAPTA (10 or 1 mM) with the slower Ca2+ buffer EGTA (5 or 0.5 mM) in the pipette solution. These data provide further evidence that endocytosis mechanisms differ in rods and cones and suggest that endocytosis in rods is regulated by both endocytic load and local Ca 2+ levels.

KW - Endocytosis

KW - Exocytosis

KW - Retina

KW - Ribbon synapse

KW - Rod photoreceptors

UR - http://www.scopus.com/inward/record.url?scp=84901323790&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84901323790&partnerID=8YFLogxK

U2 - 10.1017/S095252381400011X

DO - 10.1017/S095252381400011X

M3 - Article

C2 - 24735554

AN - SCOPUS:84901323790

VL - 31

SP - 227

EP - 235

JO - Visual Neuroscience

JF - Visual Neuroscience

SN - 0952-5238

IS - 3

ER -