Correlation between the effect of the anti-neoplastic ether lipid 1-O-octadecyl-2-O-methyl-glycero-3-phosphocholine on the membrane and the activity of protein kinase Calpha.
The antineoplastic ether phospholipid 1-O-octadecyl-2-O-methyl-sn-glycero-3-phophocholine (ET-18-OCH3) was incorporated into dimyristoylglycerophosphocholine (Myr2Gro-PCho)/dimyristoylglycerophosphoserine (Myr2Gro-PSer) (4 : 1 molar ratio) mixtures. Electron microscopy showed that the addition of ET-18-OCH3 reduced the size of the vesicles. Small vesicles could be detected even at 60 mol% ET-18-OCH3. Sedimentation studies showed the increasing presence of phospholipids in the supernatant, while turbidity measurements indicated a decrease in absorbance as the ET-18-OCH3 concentration was increased. These findings may be explained by the formation of small vesicles and/or mixed micelles. Infrared spectroscopy showed that at 60 mol% the fluidity of the membrane was considerably increased at temperatures below the phase transition, with only a small increase in the proportion of gauche isomers after the gel-to-fluid phase transition of this sample. On the other hand, protein kinase Calpha (PKCalpha) activity progressively decreased when ET-18-OCH3 was incorporated into multilamellar vesicles, reaching a minimum value at 20 mol%, this inhibition being attributed to the modification of the membrane produced by a cone-shaped molecule. At higher concentrations, however, ET-18-OCH3 activated the enzyme with a maximum being attained at 50 mol%. This activation being attributed to the formation of small vesicles and/or micelles. At still higher concentrations of ET-18-OCH3 the enzyme was once again inhibited, inhibition being almost complete at 80 mol%. When PKC was assayed using large unilamellar vesicles a slight activation was observed at very low ET-18-OCH3 concentrations.
Aroca
J D
JD
Departamento de Bioquímica y Biología Molecular 'A', Facultad de Veterinaria, Universidad de Murcia, Apartado de Correos, Murcia, Spain.
Sánchez-Piñera
P
P
Corbalán-García
S
S
Conesa-Zamora
P
P
de Godos
A
A
Gómez-Fernández
J C
JC
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D007527:Isoenzymes / Q000037:antagonists & inhibitors* / Q000378:metabolism; D008854:Microscopy, Electron; D019906:Nuclear Magnetic Resonance, Biomolecular; D010742:Phospholipid Ethers / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051571:Protein Kinase C-alpha; D017550:Spectroscopy, Fourier Transform Infrared
D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D010742:Phospholipid Ethers; C026659:edelfosine; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha