Susceptibility of cerebellar granule neurons from GM2/GD2 synthase-null mice to apoptosis induced by glutamate excitotoxicity and elevated KCl: rescue by GM1 and LIGA20.
Our previous study showed an impaired regulation of Ca(2+) homeostasis in cultured cerebellar granule neurons (CGN) from neonatal mice lacking GM2, GD2 and all gangliotetraose gangliosides, due to disruption of the GM2/GD2 synthase (GalNAc-T) gene. In the presence of depolarizing concentration (55 mM) K(+), these cells showed persistent elevation of intracellular Ca(2+) ([Ca(2+)]( i )) leading to apoptosis and cell destruction. This was in contrast to CGN from normal littermates whose survival was enhanced by high K(+). In this study we demonstrate that glutamate has the same effect as K(+) on CGN from these ganglioside-deficient knockout (KO) mice and that apoptosis in both cases is averted by exogenous GM1. Even more effective rescue was obtained with LIGA20, a semi-synthetic derivative of GM1. LC(50) of glutamate in the KO cells was 3.1 microM, compared to 46 microM in normal CGN. [Ca(2+)]( i ) measurement with fura-2 revealed no difference in glutamate-stimulated Ca(2+) influx between the 2 cell types. However, reduction of [Ca(2+)]( i ) following application of Mg(2+) was significantly impaired in the mutant CGN. The rescuing effects of exogenous GM1 and LIGA20 corresponded to their ability to restore Ca(2+) homeostasis. The greater potency of LIGA20 is attributed to its greater membrane permeability with resultant ability to insert into both plasma and nuclear membranes at low concentration (</=1 microM); GM1 at the same concentration was incorporated only into the plasma membrane and required much higher concentration to influence Ca(2+) homeostasis and CGN viability.
Wu
Gusheng
G
Department of Neurology and Neurosciences, New Jersey Medical School-UMDNJ, Newark, New Jersey 07103, USA.
Lu
Zi-Hua
ZH
Xie
Xin
X
Ledeen
Robert W
RW
D000818:Animals; D002470:Cell Survival; D002531:Cerebellum / Q000166:cytology* / Q000201:enzymology; D003594:Cytoplasmic Granules / Q000201:enzymology*; D005677:G(M1) Ganglioside / Q000031:analogs & derivatives* / Q000494:pharmacology*; D018698:Glutamic Acid / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D017350:N-Acetylgalactosaminyltransferases / Q000235:genetics / Q000502:physiology*; D009474:Neurons / Q000166:cytology*; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology*
C086919:LIGA 20; D005677:G(M1) Ganglioside; D018698:Glutamic Acid; D017350:N-Acetylgalactosaminyltransferases; C023220:(N-acetylneuraminyl)-galactosylglucosylceramide N-acetylgalactosaminyltransferase; D013110:Sphingosine