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Mutant NG108‐15 cells (NG‐CR72) deficient in GM1 synthase respond aberrantly to axonogenic stimuli and are vulnerable to calcium‐induced apoptosis: they are rescued with LIGA‐20
Author(s) -
Wu Gusheng,
Lu ZiHua,
Xie Xin,
Li Libin,
Ledeen Robert W.
Publication year - 2001
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.2001.00036.x
Subject(s) - apoptosis , mutant , liga , atp synthase , calcium , biology , microbiology and biotechnology , calcium signaling , neuroscience , signal transduction , medicine , genetics , gene , pathology , alternative medicine , fabrication
The neuroblastoma × glioma NG108‐15 hybrid cell line, a widely used model for the study of neuronal differentiation, contains a variety of gangliosides including GM1 and its sialosylated derivative, GD1a. To investigate the role of these a‐series gangliotetraose gangliosides in neuritogenesis, we have obtained a mutated subclone of NG108‐15 that is deficient in that family of gangliosides. NG108‐15 cells were grown in the presence of cholera toxin, which killed the large majority of cells, and from the cholera‐resistant survivors we isolated a clone, NG‐CR72, that lacks GM1 and GD1a in the plasma and nuclear membranes. GM2 concentration was significantly higher in the plasma membrane. Enzyme assay indicated deficiency of UDP‐Gal:GM2 galactosyltransferase (GM1 synthase), which was confirmed by incorporation studies with [ 3 H]sphingosine. These cells resembled wild‐type NG108‐15 in extending dendritic processes in response to dendritogenic agents (retinoic acid, dibutyryl cAMP) but responded aberrantly to axonogenic stimuli (KCl, ionomycin) by extending unstable neurites that showed the cytoskeletal staining characteristic of dendrites. Moreover, mutant cells treated with the Ca 2+ ‐elevating axonogenic agents underwent apoptosis over time, attributed to dysfunction of Ca 2+ regulatory mechanisms normally mediated by GM1. Such agents caused dramatic and sustained elevation of intracellular Ca 2+ in mutant cells, in contrast to modest and temporary elevation in wild‐type cells. Exogenous GM1, inserted into the plasma membrane, had no discernable protective effect on NG‐CR72 cells whereas LIGA‐20, a membrane‐permeant derivative of GM1 that entered both plasma and nuclear membranes, blocked apoptosis, permitted extension of stable neurites, and attenuated the abnormal elevation of intracellular Ca 2+ .