Ca(2+)-independent phospholipase A2 participates in the vesicular transport of milk proteins.
Changes in the lipid composition of intracellular membranes are believed to take part in the molecular processes that sustain traffic between organelles of the endocytic and exocytic transport pathways. Here, we investigated the participation of the calcium-independent phospholipase A2 in the secretory pathway of mammary epithelial cells. Treatment with bromoenol lactone, a suicide substrate which interferes with the production of lysophospholipids by the calcium-independent phospholipase A2, resulted in the reduction of milk proteins secretion. The inhibitor slowed down transport of the caseins from the endoplasmic reticulum to the Golgi apparatus and affected the distribution of p58 and p23, indicating that the optimal process of transport of these proteins between the endoplasmic reticulum, the endoplasmic reticulum/Golgi intermediate compartment and/or the cis-side of the Golgi was dependent upon the production of lysolipids. Moreover, bromoenol lactone was found to delay the rate of protein transport from the trans-Golgi network to the plasma membrane. Concomitantly, membrane-bound structures containing casein accumulated in the juxtanuclear Golgi region. We concluded from these results that efficient formation of post-Golgi carriers also requires the phospholipase activity. These data further support the participation of calcium-independent phospholipase A2 in membrane trafficking and shed a new light on the tubulo/vesicular transport of milk protein through the secretory pathway.
Péchoux
Christine
C
Institut National de la Recherche Agronomique, Laboratoire de Génomique et Physiologie de la Lactation. F-78352 Jouy-en-Josas Cedex, France.
Boisgard
Raphaël
R
Chanat
Eric
E
Lavialle
Françoise
F
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D006056:Golgi Apparatus / Q000378:metabolism; D042541:Intracellular Space / Q000378:metabolism; D007774:Lactation; D008321:Mammary Glands, Animal / Q000378:metabolism* / Q000648:ultrastructure; D008894:Milk Proteins / Q000378:metabolism*; D009281:Naphthalenes / Q000494:pharmacology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000378:metabolism*; D054467:Phospholipases A2; D011753:Pyrones / Q000494:pharmacology; D011817:Rabbits; D051381:Rats; D017208:Rats, Wistar; D021601:trans-Golgi Network / Q000378:metabolism
D008894:Milk Proteins; D009281:Naphthalenes; D010726:Phosphodiesterase Inhibitors; D011753:Pyrones; C068314:6-(bromomethylene)tetrahydro-3-(1-naphthaleneyl)-2H-pyran-2-one; D010741:Phospholipases A; D054467:Phospholipases A2