Evidence for secretory pathway localization of a voltage-dependent anion channel isoform

Evidence for secretory pathway localization of a voltage-dependent anion channel isoform

^*Institute of Pathology, University Hospital Rheinisch-Westfälische Technische Hochschule Aachen, Pauwelstrasse 30, D-52074 Aachen, Germany; ^†Albert Einstein College of Medicine, Department of Neuroscience, 1300 Morris Park Avenue, Bronx, NY 10461; ^‡Bioscience Institute, Department of Physiology, University of Sao Paulo, Sao Paulo CP11461, Brazil; and ^§Institute for Anatomy, Department of Neuroanatomy and Molecular Brain Research, Ruhr-Universität Bochum, Universitätsstrasse 150, D-44801 Bochum, Germany

Edited by Harvey F. Lodish, Massachusetts Institute of Technology, Cambridge, MA, and approved January 21, 2000 (received for review June 14, 1999)

Abstract

Voltage-dependent anion channels (VDACs) are pore-forming proteins (porins) that form the major pathway for movement of adenine nucleotides through the outer mitochondrial membrane. Electrophysiological studies indicate that VDAC-like channel activity is also prevalent in the cell membranes of many mammalian cells. However, the multitopological localization of porins outside the mitochondrion has remained an extremely controversial issue. Herein, we show that usage of two alternative first exons of the murine VDAC-1 gene leads to expression of two porins differing within their N termini. One porin (plasmalemmal VDAC-1) harboring a hydrophobic leader peptide is primarily targeted through the Golgi apparatus to the cell membrane. In contrast, the second isoform lacking the N-terminal leader (mitochondrial VDAC-1) is translocated more efficiently into the outer mitochondrial membrane. Thus, our data provide unique genetic evidence in favor of a multitopological localization of a mitochondrial porin.

Footnotes

↵ ¶ To whom reprint requests should be addressed. E-mail: Rolf.Dermietzel{at}ruhr-uni.bochum.de.
This paper was submitted directly (Track II) to the PNAS office.
Article published online before print: Proc. Natl. Acad. Sci. USA, 10.1073/pnas.060242297.
Article and publication date are at www.pnas.org/cgi/doi/10.1073/pnas.060242297
Abbreviations:

VDAC,

voltage-dependent anion channel;

ER,

endoplasmic reticulum;

pl,

plasmalemmal;

mt,

mitochondrial;

RACE,

rapid amplification of cDNA ends;

RT-PCR,

reverse transcription–PCR;

kb,

kilobase;

GFP,

green fluorescent protein