title: Dietary and biliary phosphatidylcholine activates PKCζ in rat intestine.
abstract: Chylomicron output by the intestine is proportional to intestinal phosphatidylcholine (PC) delivery. Using five different variations of PC delivery to the intestine, we found that lyso-phosphatidylcholine (lyso-PC), the absorbed form of PC, concentrations in the cytosol (0 to 0.45 nM) were proportional to the input rate. The activity of protein kinase C (PKC)ζ, which controls prechylomicron output rate by the endoplasmic reticulum (ER), correlated with the lyso-PC concentration suggesting that it may be a PKCζ activator. Using recombinant PKCζ, the Km for lyso-PC activation was 1.49 nM and the Vmax 1.12 nM, more than the maximal lyso-PC concentration in cytosol, 0.45 nM. Among the phospholipids and their lyso derivatives, lyso-PC was the most potent activator of PKCζ and the only one whose cytosolic concentration suggested that it could be a physiological activator because other phospholipid concentrations were negligible. PKCζ was on the surface of the dietary fatty acid transport vesicle, the caveolin-1-containing endocytic vesicle. Once activated, PKCζ, eluted off the vesicle. A conformational change in PKCζ on activation was suggested by limited proteolysis. We conclude that PKCζ on activation changes its conformation resulting in elution from its vesicle. The downstream effect of dietary PC is to activate PKCζ, resulting in greater chylomicron output by the ER.
authors.affiliation: Division of Gastroenterology, The University of Tennessee Health Science Center, Memphis, TN.
authors.forename: Shahzad
authors.initials: S
authors.lastname: Siddiqi
authors.affiliation: Division of Gastroenterology, The University of Tennessee Health Science Center, Memphis, TN Veterans Affairs Medical Center, Memphis, TN.
authors.forename: Charles M
authors.initials: CM
authors.lastname: Mansbach
mesh_terms: D000818:Animals; D001659:Biliary Tract / Q000378:metabolism*; D018955:CD36 Antigens / Q000378:metabolism; D051242:Caveolin 1 / Q000378:metabolism; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004032:Diet; D004789:Enzyme Activation / Q000187:drug effects; D007408:Intestinal Absorption / Q000187:drug effects; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology*; D008244:Lysophosphatidylcholines / Q000494:pharmacology; D008297:Male; D020559:Monomeric GTP-Binding Proteins / Q000378:metabolism; D019301:Oleic Acid / Q000378:metabolism; D010713:Phosphatidylcholines / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D011487:Protein Conformation; D011493:Protein Kinase C / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D022161:Transport Vesicles / Q000187:drug effects / Q000378:metabolism; D000099221:Protein Kinase C zeta
chemical_list: D018955:CD36 Antigens; D051242:Caveolin 1; D008244:Lysophosphatidylcholines; D020559:Monomeric GTP-Binding Proteins; D019301:Oleic Acid; D010713:Phosphatidylcholines; D011493:Protein Kinase C; D000099221:Protein Kinase C zeta; C000601317:Sar1b protein, mouse
keywords: caveolin-1-containing endocytic vesicle; chylomicrons; lyso-phosphatidylcholine; protein kinase C zeta