R25 is an intracellular membrane receptor for a snake venom secretory phospholipase A(2).
Ammodytoxin is a presynaptically neurotoxic (beta-neurotoxic) snake venom secretory phospholipase A(2) (sPLA(2)). We detected a 25 kDa protein which binds the toxin with very high affinity (R25) in porcine cerebral cortex. Here we show that R25 is an integral membrane protein with intracellular localisation. It is the first sPLA(2) receptor known to date that localises to intracellular membranes. Centrifugation on sucrose gradients was used to fractionate porcine cerebral cortex. The subcellular composition of the fractions was determined by following the distribution of organelle-specific markers. The distribution of R25 in the fractions matched the distribution of the mitochondrial marker succinate dehydrogenase, but not the markers for plasma membrane, lysosomes, endoplasmic reticulum, synaptic and secretory vesicles. R25 most likely resides in mitochondria, which are known to be targets for sPLA(2) neurotoxins in the nerve ending and are potentially implicated in the process of beta-neurotoxicity.
Department of Biochemistry and Molecular Biology, Jozef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia.
Jernej
J
Sribar
Alenka
A
Copic
Mateja
M
Poljsak-Prijatelj
Jost
J
Kuret
Uros
U
Logonder
Franc
F
Gubensek
Igor
I
Krizaj
D009597:4-Nitrophenylphosphatase / Q000032:analysis / Q000378:metabolism; D000818:Animals; D002403:Cathepsins / Q000032:analysis / Q000378:metabolism; D002540:Cerebral Cortex / Q000737:chemistry / Q000648:ultrastructure; D054501:Group II Phospholipases A2; D007425:Intracellular Membranes / Q000378:metabolism*; D008970:Molecular Weight; D009251:NADPH-Ferrihemoprotein Reductase / Q000032:analysis / Q000378:metabolism; D015388:Organelles / Q000201:enzymology; D010741:Phospholipases A / Q000378:metabolism*; D011485:Protein Binding; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D054507:Receptors, Phospholipase A2; D012910:Snake Venoms / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism; D013385:Succinate Dehydrogenase / Q000032:analysis / Q000378:metabolism; D013552:Swine; D014757:Viper Venoms / Q000378:metabolism*
D011956:Receptors, Cell Surface; D054507:Receptors, Phospholipase A2; D012910:Snake Venoms; D014757:Viper Venoms; D013385:Succinate Dehydrogenase; D009251:NADPH-Ferrihemoprotein Reductase; D010741:Phospholipases A; D054501:Group II Phospholipases A2; C060161:ammodytoxin C; D009597:4-Nitrophenylphosphatase; D002403:Cathepsins