The effect of calcium levels on synaptic proteins. A study on VAT-1 from Torpedo

M. Linial*, O. Levius, N. Ilouz, D. Parnas

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

In this study we compare major synaptic proteins from Torpedo electric organ to their homologues from mammalian brain. Most of these proteins are members of small gene families. We demonstrate a high degree of evolutionary conservation of most synaptic proteins. However, in the electric organ each gene family is represented only by a single member. We focus on VAT-1, a major protein of the vesicle membrane in Torpedo. VAT-1 is located on the synaptic vesicle membrane and is highly concentrated on the plasma membrane following the application of α-latrotoxin. Taking advantage of the relative simplicity of Torpedo synapses, we performed an in vitro study on the properties of VAT-1 affected by changes in Ca2+ levels. VAT-1 is a low affinity Ca2+ binding protein whose ability to bind Ca2+ resides mainly, but not entirely, on the carboxy-terminal domain of the protein. In the presence of Ca2+, the protein is organized in a high molecular mass complex, which is destabilized by depleting Ca2+. This effect occurs only by chelating Ca2+ ions, but not with other divalent ions. VAT-1 is not complexed to any of the proteins which were implicated in the docking/fusion complex such as VAMP, synaptophysin or syntaxin, regardless of Ca2+ levels. Dependence of the stability of protein complexes on Ca2+ levels is also demonstrated on Torpedo n-Sec1. The possible physiological implications of such Ca2+ dependence are discussed.

Original languageAmerican English
Pages (from-to)103-112
Number of pages10
JournalJournal of Physiology Paris
Volume89
Issue number2
DOIs
StatePublished - 1995

Bibliographical note

Funding Information:
We thank H Boschwitz for technical assistancei n preparation of VAT-I antibodiesa nd N Feinstein for assistancei n the immunoelectron microscopy. We are grateful to WS Trimble (University of Toronto. Ontario) and to Z Lev (Technion, Israel) for their kind contributiono f antibodies againstT orpedo VAMP and Drosoplzik~r op, respectivelyW. e thank Alomone Lab (Jerusalem)f or providing us with a-la-trotoxin and the Smith laboratoryi n the Hebrew University for the use of microscopy facilities. This work was partially supportedb y the Ministry of Science and the Arts (4363-I-93). by the German-IsraeliF oundation( I-299-023)a nd by the Israel Science Foundation ( 152/93).

Keywords

  • Ca regulation
  • SNARE hypothesis
  • acetylcholine release
  • elasmobranch
  • synaptic vesicle

Fingerprint

Dive into the research topics of 'The effect of calcium levels on synaptic proteins. A study on VAT-1 from Torpedo'. Together they form a unique fingerprint.

Cite this