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Apical release of base‐labile fatty acyl groups commensurate with stimulation of glycoprotein sialosyl Lewis a secretion in colorectal carcinoma cells
Author(s) -
Liepkalns V. A.,
Eboue D.,
Kuksis A.,
Beringer T.,
IcardLiepkalns C.
Publication year - 1995
Publication title -
international journal of cancer
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.475
H-Index - 234
eISSN - 1097-0215
pISSN - 0020-7136
DOI - 10.1002/ijc.2910620109
Subject(s) - secretion , stimulation , glycoprotein , chemistry , medicine , endocrinology , biochemistry , biology , cancer research
Abstract The rate of polarized secretion of a putative adhesion ligand, sialosyl Lewis a (19–9), by SW1116 colorectal carcinoma cells is stimulated at least 20‐fold after pre‐incubation with, and the incorporation of, retinoic acid (RA). In order to investigate the possible involvement of fatty acylation in the export of the epitope, purified ligandsfrom carcinoma‐cell membranes, membrane subfractions and media were analyzed during RA‐induced secretion. Incorporation of radioactivity from ( 3 H)palmitate into membrane subfractions and purified sialosyl Lewis a antigenic molecular species of Mr > 150,000 (SiaLeams) was stimulated by RA treatment. Most of the intracellular lipid radioactivity which bound to solid‐phase 19–9 antibody behaved chromato‐graphically, either like ganglioside or like NH 2 OH‐labile acyl groups, but most of the ( 3 H) bound to SiaLeams of post‐incubation media behaved like base‐labile fatty acyl groups, or free fatty acid. Release of base‐labile lipid radioactivity after 3 hr (associated with antigen) was almost exclusively into the apical media of membrane inserts. Gas‐liquid chromatography/mass spec, analyses of purified Sialeams revealed the presence of palmitate (16:0), as well as stearate (18:0) and oleate (18:1) fatty acyl groups. Our results suggest that fatty acylation of SiaLeams may be co‐ordinated with alterations in glycosylation and participate in directing these molecules to the apical surface. Lipid analyses were consistent with ganglioside chaperonage of SiaLeams to the apical surface, where N‐fatty‐acylated gangliosides remain for the most part integrated into the bilayer, but some oxyester or thioester bonds may be cleaved to permit release of SiaLeams to the apical medium. © 1995 Wiley‐Liss Inc.