A novel arachidonic acid-selective cytosolic PLA2 contains a Ca(2+)-dependent translocation domain with homology to PKC and GAP.
We report the cloning and expression of a cDNA encoding a high molecular weight (85.2 kd) cytosolic phospholipase A2 (cPLA2) that has no detectable sequence homology with the secreted forms of PLA2. We show that cPLA2 selectively cleaves arachidonic acid from natural membrane vesicles and demonstrate that cPLA2 translocates to membrane vesicles in response to physiologically relevant changes in free calcium. Moreover, we demonstrate that an amino-terminal 140 amino acid fragment of cPLA2 translocates to natural membrane vesicles in a Ca(2+)-dependent fashion. Interestingly, we note that this 140 amino acid domain of cPLA2 contains a 45 amino acid region with homology to PKC, p65, GAP, and PLC. We suggest that this homology delineates a Ca(2+)-dependent phospholipid-binding motif, providing a mechanism for the second messenger Ca2+ to translocate and activate cytosolic proteins.
Clark
J D
JD
Genetics Institute, Inc., Cambridge, Massachusetts 02140.
Lin
L L
LL
Kriz
R W
RW
Ramesha
C S
CS
Sultzman
L A
LA
Lin
A Y
AY
Milona
N
N
Knopf
J L
JL
D000595:Amino Acid Sequence; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D002118:Calcium / Q000502:physiology; D002451:Cell Compartmentation; D002462:Cell Membrane / Q000201:enzymology; D003001:Cloning, Molecular; D003600:Cytosol / Q000201:enzymology; D020690:GTPase-Activating Proteins; D006801:Humans; D008563:Membrane Lipids / Q000378:metabolism; D008969:Molecular Sequence Data; D010741:Phospholipases A / Q000235:genetics* / Q000378:metabolism*; D054467:Phospholipases A2; D010743:Phospholipids / Q000378:metabolism; D011493:Protein Kinase C / Q000737:chemistry; D011506:Proteins / Q000737:chemistry; D013379:Substrate Specificity; D010738:Type C Phospholipases / Q000737:chemistry
D001095:Arachidonic Acids; D020690:GTPase-Activating Proteins; D008563:Membrane Lipids; D010743:Phospholipids; D011506:Proteins; D016718:Arachidonic Acid; D011493:Protein Kinase C; D010741:Phospholipases A; D054467:Phospholipases A2; D010738:Type C Phospholipases; D002118:Calcium