A novel multiprotein complex is required to generate the prechylomicron transport vesicle from intestinal ER.
Dietary lipid absorption is dependent on chylomicron production whose rate-limiting step across the intestinal absorptive cell is the exit of chylomicrons from the endoplasmic reticulum (ER) in its ER-to-Golgi transport vesicle, the prechylomicron transport vesicle (PCTV). This study addresses the composition of the budding complex for PCTV. Immunoprecipitation (IP) studies from rat intestinal ER solubilized in Triton X-100 suggested that vesicle-associated membrane protein 7 (VAMP7), apolipoprotein B48 (apoB48), liver fatty acid-binding protein (L-FABP), CD36, and the COPII proteins were associated on incubation of the ER with cytosol and ATP. This association was confirmed by chromatography of the solubilized ER over Sephacryl S400-HR in which these constituents cochromatographed with an apparent kDa of 630. No multiprotein complex was detected when the ER was chromatographed in the absence of PCTV budding activity (resting ER or PKCzeta depletion of ER and cytosol). Treatment of the ER with anti-apoB48 or anti-VAMP7 antibodies or using gene disrupted L-FABP or CD36 mice all significantly inhibited PCTV generation. A smaller complex (no COPII proteins) was formed when only rL-FABP was used to bud PCTV. The data support the conclusion that the PCTV budding complex in intestinal ER is composed of VAMP7, apoB48, CD36, and L-FABP, plus the COPII proteins.
Division of Gastroenterology, Department of Medicine, University of Tennessee Health Science Center, Memphis, TN, USA.
Shahzad
S
Siddiqi
Umair
U
Saleem
Nada A
NA
Abumrad
Nicholas O
NO
Davidson
Judith
J
Storch
Shadab A
SA
Siddiqi
Charles M
CM
Mansbach
D000818:Animals; D053283:Apolipoprotein B-48 / Q000378:metabolism; D001692:Biological Transport; D018955:CD36 Antigens / Q000378:metabolism; D022181:COP-Coated Vesicles / Q000378:metabolism; D002914:Chylomicrons / Q000378:metabolism*; D004041:Dietary Fats / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D050556:Fatty Acid-Binding Proteins / Q000378:metabolism; D007408:Intestinal Absorption / Q000502:physiology*; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000166:cytology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018832:Molecular Chaperones / Q000378:metabolism; D046912:Multiprotein Complexes / Q000378:metabolism*; D050683:R-SNARE Proteins / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D022161:Transport Vesicles / Q000378:metabolism*; D000099221:Protein Kinase C zeta
D053283:Apolipoprotein B-48; D018955:CD36 Antigens; D002914:Chylomicrons; D004041:Dietary Fats; D050556:Fatty Acid-Binding Proteins; D018832:Molecular Chaperones; D046912:Multiprotein Complexes; D050683:R-SNARE Proteins; C493321:Fabp1 protein, rat; C490392:Prkcz protein, rat; D000099221:Protein Kinase C zeta; C496926:Vamp7 protein, rat