HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Thompson, R. J. Articles by Caldwell, J. H. Search for Related Content PubMed PubMed Citation Articles by Thompson, R. J. Articles by Caldwell, J. H.

MEMBRANE TRANSPORTERS, ION CHANNELS, AND PUMPS

Anion channels transport ATP into the Golgi lumen

Department of Cell and Developmental Biology, University of Colorado Health Sciences Center, Aurora, Colorado

Submitted 1 December 2004 ; accepted in final form 2 September 2005

Anion channels provide a pathway for Cl^– influx into the lumen of the Golgi cisternae. This influx permits luminal acidification by the organelle's H⁺-ATPase. Three different experimental approaches, electrophysiological, biochemical, and proteomic, demonstrated that two Golgi anion channels, GOLAC-1 and GOLAC-2, also mediate ATP anion transport into the Golgi lumen. First, GOLAC-1 and -2 were incorporated into planar lipid bilayers, and single-channel recordings were obtained. Low ionic activities of K₂ATP added to the cis-chamber directly inhibited the Cl^– subconductance levels of both channels, with K_m values ranging from 16 to 115 µM. Substitution of either K₂ATP or MgATP for Cl^– on the cis, trans, or both sides indicated that ATP is conducted by the channels with a relative permeability sequence of Cl^– > ATP^4– > MgATP^2–. Single-channel currents were observed at physiological concentrations of Cl^– and ATP, providing evidence for their importance in vivo. Second, transport of [-³²P]ATP into sealed Golgi vesicles that maintain in situ orientation was consistent with movement through the GOLACs because it exhibited little temperature dependence and was saturated with an apparent K_m = 25 µM. Finally, after transport of [-³²P]ATP, a protease-protection assay demonstrated that proteins are phosphorylated within the Golgi lumen, and after SDS-PAGE, the proteins in the phosphorylated bands were identified by mass spectrometry. GOLAC conductances, [-³²P]ATP transport, and protein phosphorylation have identical pharmacological profiles. We conclude that the GOLACs play dual roles in the Golgi complex, providing pathways for Cl^– and ATP influx into the Golgi lumen.

Golgi complex; Cl channel; mass spectrometry; phosphorylation

This article has been cited by other articles:

				A. Goytain and G. A. Quamme Identification and characterization of a novel family of membrane magnesium transporters, MMgT1 and MMgT2 Am J Physiol Cell Physiol, February 1, 2008; 294(2): C495 - C502. [Abstract] [Full Text] [PDF]