Phospholipase A2 Antagonists Inhibit Constitutive Retrograde Membrane Traffic to the Endoplasmic Reticulum
ABSTRACT Eukaryotic cells contain a variety of cytoplasmic Ca2+-dependent and Ca2+-independent phospholipase A2s (PLA2s; EC 18.104.22.168.3). However, the physiological roles for many of these ubiquitously-expressed enzymes is unclear or not known. Recently, pharmacological studies have suggested a role for Ca2+-independent PLA2 (iPLA2) enzymes in governing intracellular membrane trafficking events in general and regulating brefeldin A (BFA)-stimulated membrane tubulation and Golgi-to-endoplasmic reticulum (ER) retrograde membrane trafficking, in particular. Here, we extend these studies to show that membrane-permeant iPLA2 antagonists potently inhibit the normal, constitutive retrograde membrane trafficking from the trans-Golgi network (TGN), Golgi complex, and the ERGIC-53-positive ER-Golgi-intermediate compartment (ERGIC), which occurs in the absence of BFA. Taken together, these results suggest that iPLA2 enzymes play a general role in regulating, or directly mediating, multiple mammalian membrane trafficking events.
Article: Arachidonic acid metabolism.[show abstract] [hide abstract]
ABSTRACT: Arachidonic acid metabolites can act as tumor promoters and can affect growth and metastases of tumors in three ways: (a) Prostacyclin inhibits and thromboxane facilitates platelet-tumor cell interactions and, thereby, tumor cell invasiveness; (b) the cytoprotective action of prostaglandins contributes to epithelial cell integrity and influences tissue response to tumor-promoting agents; and (c) lipoxygenase products may act as tumor promoters.Preventive Medicine 08/1987; 16(4):503-9. · 3.50 Impact Factor
- Journal of Biological Chemistry - J BIOL CHEM. 01/1995; 270(6):2880-2880.
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ABSTRACT: A trifluoromethyl ketone analogue of arachidonic acid in which the COOH group is replaced with COCF3 (AACOCF3) was prepared and found to be a tight- and slow-binding inhibitor of the 85-kDa cytosolic human phospholipase A2 (cPLA2). Enzyme inhibition was observed when AACOCF3 was tested in assays using either phospholipid vesicles or phospholipid/Triton X-100 mixed micelles. The fact that the inhibition developed over several minutes in both assays establishes that AACOCF3 inhibits by direct binding to the enzyme rather than by decreasing the fraction of enzyme bound to the substrate interface. From the measured values of the inhibitor association and dissociation rate constants, an upper limit of the equilibrium dissociation constant for the Ca(2+).AACOCF3.PLA2 complex of 5 x 10(-5) mole fraction was obtained. Thus, detectable inhibition of cPLA2 by AACOCF3 occurs when this compound is present in the assay at a level of one inhibitor per several thousand substrates. Arachidonic acid analogues in which the COOH group is replaced by COCH3, CH(OH)CF3, CHO, or CONH2 did not detectably inhibit the cPLA2. The arachidonyl ketones AACOCF2CF3 and AACOCF2Cl were found by 19F NMR to be less hydrated than AACOCF3 in phospholipid/Triton X-100 mixed micelles, and compared to AACOCF3 these compounds are also weaker inhibitors of cPLA2. In keeping with the fact that cPLA2 displays substrate specificity for arachidonyl-containing phospholipids, the arachidic acid analogue C19H39COCF3 is a considerably less potent inhibitor compared to AACOCF3.(ABSTRACT TRUNCATED AT 250 WORDS)Biochemistry 07/1993; 32(23):5935-40. · 3.38 Impact Factor