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

J. Biol. Chem., Vol. 279, Issue 34, 35775-35780, August 20, 2004

This Article Full Text Full Text (PDF) All Versions of this Article: 279/34/35775    most recent M403630200v1 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 PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Kampf, J. P. Articles by Kleinfeld, A. M. Search for Related Content PubMed PubMed Citation Articles by Kampf, J. P. Articles by Kleinfeld, A. M. Social Bookmarking                      What's this?

Fatty Acid Transport in Adipocytes Monitored by Imaging Intracellular Free Fatty Acid Levels^*

J. Patrick Kampf and Alan M. Kleinfeld

From the Torrey Pines Institute for Molecular Studies, San Diego, California 92121

Transport of free fatty acids (FFA) across the adipocyte plasma membrane is critical for maintaining homeostasis. To determine the membrane's role in regulating transport we describe here the first measurements of the intracellular (unbound) FFA concentration ([FFA_i]) and their use in monitoring transport of FFA across 3T3F442A adipocytes. [FFA_i] was measured by microinjecting cells with ADIFAB, a fluorescently labeled fatty acid-binding protein that is used to measure unbound FFA levels. We used ratio fluorescence microscopy of intracellular ADIFAB to image unbound FFA levels and determined the time course of [FFA_i] in response to changing the extracellular unbound FFA concentration ([FFA_o]). [FFA_o] was clamped at defined levels using complexes of FFA and bovine serum albumin. We show that FFA influx is slow, requiring about 300 s to reach steady state (rate constant 0.02 s^-1) and saturable (K_o 200 nM). Efflux is twice as fast as influx, for zero [FFA_o], but decreases with increasing [FFA_o]. Surprisingly, at steady state [FFA_i] is 2–5-fold (average 2-fold) greater than [FFA_o] and this [FFA_i]/[FFA_o] gradient is abolished by depleting cellular ATP. Our results indicate that FFA transport across adipocyte membranes is highly regulated, involving an ATP-driven pump and a mechanism for gating efflux that is sensitive to [FFA_o]. These characteristics are well described by a membrane carrier model but are not consistent with FFA transport across the membrane's lipid phase. We suggest that these characteristics are important in regulating circulating FFA levels by the adipocyte.

Received for publication, April 1, 2004 , and in revised form, June 9, 2004.

^* This work was supported in part by National Institutes of Health Grant DK58762. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

To whom correspondence should be addressed. Tel.: 858-455-3724; Fax: 858-455-3792; E-mail: akleinfeld{at}tpims.org.

CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?

This article has been cited by other articles:

				J. P. Kampf, D. Parmley, and A. M. Kleinfeld Free fatty acid transport across adipocytes is mediated by an unknown membrane protein pump Am J Physiol Endocrinol Metab, November 1, 2007; 293(5): E1207 - E1214. [Abstract] [Full Text] [PDF]

				J. P. Kampf and A. M. Kleinfeld Is Membrane Transport of FFA Mediated by Lipid, Protein, or Both? Physiology, February 1, 2007; 22(1): 7 - 14. [Full Text] [PDF]

				A. Bonen, A. Chabowski, J. J. F. P Luiken, and J. F. C. Glatz Mechanisms and Regulation of Protein-Mediated Cellular Fatty Acid Uptake: Molecular, Biochemical, and Physiological Evidence Physiology, February 1, 2007; 22(1): 15 - 28. [Full Text] [PDF]

				J. P. Kampf, D. Cupp, and A. M. Kleinfeld Different Mechanisms of Free Fatty Acid Flip-Flop and Dissociation Revealed by Temperature and Molecular Species Dependence of Transport across Lipid Vesicles J. Biol. Chem., July 28, 2006; 281(30): 21566 - 21574. [Abstract] [Full Text] [PDF]

				A. M. Kleinfeld and C. Okada Free fatty acid release from human breast cancer tissue inhibits cytotoxic T-lymphocyte-mediated killing J. Lipid Res., September 1, 2005; 46(9): 1983 - 1990. [Abstract] [Full Text] [PDF]

				C. C. DiRusso, H. Li, D. Darwis, P. A. Watkins, J. Berger, and P. N. Black Comparative Biochemical Studies of the Murine Fatty Acid Transport Proteins (FATP) Expressed in Yeast J. Biol. Chem., April 29, 2005; 280(17): 16829 - 16837. [Abstract] [Full Text] [PDF]

				J. Liao, R. Sportsman, J. Harris, and A. Stahl Real-time quantification of fatty acid uptake using a novel fluorescence assay J. Lipid Res., March 1, 2005; 46(3): 597 - 602. [Abstract] [Full Text] [PDF]