Identification of alpha-galactose (alpha-fucose)-asialo-GM1 glycolipid expressed by subsets of rat dorsal root ganglion neurons

Distinct cell-surface glycoconjugates are expressed on specific subsets of dorsal root ganglion (DRG) neurons and DRG terminals projecting to the superficial dorsal horn of rat spinal cord (Dodd, J., and Jessell, T. M. (1985) J. Neurosci. 5, 3278-3294). Carbohydrate antigens detected by monoclonal antibodies (mAbs) TC6, KH10, and LD2 are restricted to about 20% of DRG neurons projecting to lamina IIB (dorsal), whereas antigens recognized by mAb LA4 are expressed by about 50% of DRG neurons projecting to lamina IIB (ventral). These mAbs were generated against rat pancreatic acinar cell line AR4-2J antigens. The glycolipid antigens in AR4-2J cells reacting with these mAbs have been structurally characterized by sequential hydrolysis with various exoglycosidases, immunochemical tests, linkage analysis of permethylated alditol acetates, capillary gas liquid chromatography-mass spectrometry, mass spectrometry of permethylated compounds, and by fast atom bombardment mass spectrometry of the native antigens. The structure of the major antigen (IA) in AR4-2J cells was determined to be: (formula; see text) The asialo derivative of IA and the novel disialo form of IA (Gal alpha 1----3(Fuc alpha 1----2)----GD1b) have been also identified. The DRG neurons contained only the neutral glycolipid, asialo form of IA. All these antigens reacted equivalently in the high performance thin layer chromatography-immuno overlay assay with the TC6, LD2, and LA4 mAbs. The molecular specificity of the three mAbs was determined by rection with a variety of possible antigens and appears to be the same. All three mAbs required terminal Gal alpha 1----3(Fuc alpha 1----2)Gal beta 1----3GalNAc (or 4GlcNAc) for full reactivity. Only partial reactivity was observed with compounds in which alpha-Fuc was removed. The observed restricted reactivity of mAbs TC6, LD2, and LA4 in subsets of DRG neurons and in ventral and dorsal areas of lamina IIB may be due to different topographical expression of the antigen in the neuronal membrane.