Small intestinal differentiation in human colon carcinoma HT29 cells has distinct effects on the lateral diffusion of lipids (ganglioside GM1) and proteins (HLA Class 1, HLA Class 2, and neoplastic epithelial antigens) in the apical cell membrane

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Abstract
We have studied the effect of maturation to small intestinal‐like epithelial cells of the human colonic calcinoma cell line HT29 on the lateral mobility of different representative membrane components (lipid, proteins), as assessed with fluorescence recovery after photobleaching (FRAP). Maturation was induced in vitro in the HT29 cells by replacing glucose (Glu) with galactose (Gal) in the growth medium (DMEM) during a 21‐day period. Scanning electron microscopy revealed an increased number of microvilli in the apical cell membrane, and enzyme analyses (alkaline phosphatase, aminopeptidase) in combination with aqueous countercurrent distribution, indicated that maturation was induced with DMEM‐Gal. In comparison to control cells grown in DMEM‐Glu medium, the more small intestinal‐like cells grown in DMEM‐Gal displayed no alteration of the lateral mobility of either cholera toxin (B subuni)‐labelled ganglioside GM1 (diffusion coefficient, D [x 108] = 0.8–0.9 cm2s−1; mobile fraction, R = 50‐60%) or antibody‐stained Class 2 histocompatibility (HLA‐DR) antigen (D [x 109] = 2 cm2s−1; R = 60–70%). However, antibody‐labelled β2‐microglobulin of HLA Class 1 antigen displayed increased mobility in HT29‐Gal cells; D was × 1.4 and R × 1.8 larger in the HT29‐Gal cells. By contrast, the mobility of a neoplastic antigen was reduced; D and R were × 0.60 and × 0.69 of the values seen in HT29‐Glu cells. It is thus concluded that DMEM‐Gal‐induced differentiation in confluent HT29 cells is accompanied by specific rather than general effects on the lateral mobil‐ity of different membrane components.

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