Regulation of brain m calpain Ca2+ sensitivity by mixtures of membrane lipids: activation at intracellular Ca2+ level.
Combinations of certain phospholipids and gangliosides increase the specific activity of m calpain and can activate m calpain at 1 to 10 microM Ca2+ concentration. However, this level of calcium is still greater than the normal intracellular calcium level. We have used combinations of lipids to demonstrate the m calpain activity at the physiological Ca2+ level. GD1a (100 microM) and cerebroside (Cerb; 750 microM; 1:7.5) mixture was the most effective. At 0.5 microM to 1.0 microM Ca2+ concentrations, 15-20% of the maximal activity was detected for the purified myelin and cytosolic m calpains. Other combinations were GD1a (100 microM), GM1 (100 microM), Cerb (750 microM), sulfatide (Sulf; 750 microM), and phosphatidylinositol (PI; 300 microM) at a ratio of 1:1: 7.5:7.5:3, respectively. These lipid mixtures stimulated calpain activity at three- to tenfold less calcium concentration than control. The other mixtures, including GD1a:Sulf (1:9) > GD1a:PI (1:4) > PI:Sulf (1:5) > Cerb:Sulf (1:5) and PI:Cerb (1:2.5), also stimulated calpain activity at 1.0 microM Ca2+ concentration. Triton X-100, oxidized glutathione (GSSG), and calpain activator did not affect the Ca2+ requirement. Liposomes containing GD1a, Cerb, and m calpain also showed recognizable calpain activity at a significantly reduced Ca2+ concentration (0.4 microM), confirming the glycolipid-mediated enzyme modulation. These studies indicate that specific lipid mixtures can stimulate m calpain activity at an intracellular level of Ca2+.
Chakrabarti
A K
AK
Department of Neurology, Medical University of South Carolina, Charleston 29425, USA.
Dasgupta
S
S
Gadsden
R H
RH
Hogan
E L
EL
Banik
N L
NL
D000818:Animals; D001921:Brain / Q000201:enzymology*; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology*; D002154:Calpain / Q000378:metabolism*; D002417:Cattle; D002554:Cerebrosides / Q000494:pharmacology*; D003600:Cytosol / Q000201:enzymology; D005732:Gangliosides / Q000494:pharmacology*; D007700:Kinetics; D008563:Membrane Lipids / Q000494:pharmacology*; D009186:Myelin Sheath / Q000201:enzymology; D010716:Phosphatidylinositols / Q000494:pharmacology; D013433:Sulfoglycosphingolipids / Q000494:pharmacology
D002554:Cerebrosides; D005732:Gangliosides; D008563:Membrane Lipids; D010716:Phosphatidylinositols; D013433:Sulfoglycosphingolipids; C021298:ganglioside, GD1a; D002154:Calpain; D002118:Calcium