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Journal of Lipid Research, Vol. 47, 1928-1939, September 2006
Copyright © 2006 by American Society for Biochemistry and Molecular Biology

Colocalization of SCD1 and DGAT2: implying preference for endogenous monounsaturated fatty acids in triglyceride synthesis

Weng Chi Man^*, Makoto Miyazaki^1,*, Kiki Chu^* and James Ntambi^1,*,

^* Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706
Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI 53706

Published, JLR Papers in Press, June 2, 2006.

¹ To whom correspondence should be addressed. e-mail: miyazakim{at}biochem.wisc.edu (M.M.); ntambi{at}biochem.wisc.edu (J.N.)

Stearoyl-coenzyme A desaturase (SCD) is an endoplasmic reticulum (ER) protein that catalyzes the 9-cis desaturation of saturated fatty acids. Mice with targeted disruption in SCD1 (Scd1^–/–) have significant reduction in the tissue content of triglycerides, suggesting that monounsaturated fatty acids endogenously synthesized by SCD1 are important for triglyceride synthesis. Acyl-coenzyme A:diacylglycerol acyltransferase (DGAT) is the enzyme that catalyzes the final reaction in the synthesis of triglycerides. The lack of DGAT2, one of the two DGAT isoforms, results in almost a complete loss of tissue triglycerides. We hypothesize that SCD1 participates in triglyceride synthesis by providing a more accessible pool of monounsaturated fatty acids through substrate channeling. In this study, we test whether SCD1 is proximal to DGAT2 by colocalization study with confocal microscopy, coimmunoprecipitation, and fluorescence resonance energy transfer using HeLa cells as the model of study. All of the results suggest that SCD1 and DGAT2 are located very close to each other in the ER, which is a very important criterion for the channeling of substrate. By performing subcellular fractionation using mouse livers, we also show, for the first time, that SCD is present in the mitochondria-associated membrane.

Supplementary key words stearoyl-coenzyme A desaturase 1 • acyl-coenzyme A:diacylglycerol acyltransferase 2 • fluorescence resonance energy transfer

Abbreviations: CFP, cyan fluorescent protein; DGAT, acyl-coenzyme A:diacylglycerol acyltransferase; ER, endoplasmic reticulum; FRET, fluorescence resonance energy transfer; MAM, mitochondria-associated membrane; SCD, stearoyl-coenzyme A desaturase; YFP, yellow fluorescent protein

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