Expression of dipeptidyl aminopeptidase IV during enterocytic differentiation of human colon cancer (Caco‐2) cells

Abstract

The human colon cancer cell line Caco-2 spontaneously differentiates to an enterocyte-like cell after confluence under standard culture conditions. This is characterized by polarization of the cell monolayer with the appearance of tight junctions, a brush border membrane and expression of brush-border-membrane-associated hydrolases. Studies have shown that differentiated Caco-2 cells express relatively high levels of dipeptidyl aminopeptidase IV (DPP IV) when compared with other enzymes. However, the biochemical mechanisms involved in the expression of DPP IV in differentiated cells are currently unknown. Therefore, the biosynthesis and expression of membrane-associated DPP IV in undifferentiated (0 day confluent) and differentiated (14 day confluent) Caco-2 cells were examined. Though levels of DPP IV activity in differentiated cells was 5- to 6-fold higher than undifferentiated cells, there was only a 1.6-fold difference in the synthetic rate. Post-translational processing of newly synthesized DPP IV occurred at a slower rate in differentiated cells, though there were no major differences in the type or degree of glycosylation. A comparison of the degradation rates revealed that they were similar with a half-life of approximately 8 to 10 days. We conclude that the high levels of DPP IV expressed in differentiated Caco-2 cells is primarily due to an increase in enzyme synthesis. In addition, accumulation of the enzyme is aided by its slow turnover rate.

Differential response to keratinocyte growth factor receptor and epidermal growth factor receptor ligands of proliferating and differentiating intestinal epithelial cells

“…Previous studies from our group have shown that: (a) up-regulation of KGFRs can be observed in human primary cultured keratinocytes during in vitro differentiation induced by high Ca 2þ concentrations (Marchese et al, 1997) and (b) the confluence-induced differentiation of the non-transformed human keratinocyte cell line HaCaT causes an increase of functional KGFRs on the plasma membranes of the suprabasal cells which appears related with retention of the proliferative activity (Capone et al, 2000). Here we report that also for the intestinal epithelial cell line Caco-2, a widely used in vitro model of intestinal proliferation and differentiation (Chantret et al, 1988;Yoshioka et al, 1991), as well as of brush border assembly (Peterson and Mooseker, 1993), the expression of KGFRs is up-modulated during the initial spontaneous differentiation of the cells, as shown by the results obtained either from the biochemical Western blot detection of the total KGFR protein or from the immunofluorescence and immunoelectron microscopic analysis of the expression and distribution of the receptors on the cell plasma membranes (Fig. 8).…”

Inhibition of aberrant crypt growth by non‐steroidal anti‐inflammatory agents and differentiation agents in the rat colon

“…The other agents tested in this study, 13-cis-retinoic acid and 4-hydroxyphenretanimide, were effective in inhibiting the formation of aberrant crypts, with 13-cis-retinoic acid being the much more effective compound. Both in cell culture and in a wide variety of animal tissues 13-cis-rctinoic acid is a powerful differentiating agent (De Luca, 1991;Yoshioka et al, 1991). It has bcen shown to inhibit cancer in the rat colon, but its effects in the human colon have not been directly tested (O'Dwyer et al, 1987).…”

Cytotoxic and Allergenic Potential of Bioactive Proteins and Peptides

“…IgE binding epitopes are widely spread all along the -lactoglobulin and -lactalbumin molecules as evidenced by using tryptic and synthetic peptides or overlapping peptides. The best recognized peptides, by more than 90% of the patients, are BLG fragments (41)(42)(43)(44)(45)(46)(47)(48)(49)(50)(51)(52)(53)(54)(55)(56)(57)(58)(59)(60), and (149)(150)(151)(152)(153)(154)(155)(156)(157)(158)(159)(160)(161)(162), each of them accounting for 10 to 15% of whole BLG immunoreactivity [147]. In addition the C-terminal fragment (149)(150)(151)(152)(153)(154)(155)(156)(157)(158)(159)(160)…”

“…DPP IV is synthesized within the cell as a dimeric glycoprotein and is subsequently integrated in the apical cell membrane (brush border), with its active site being situated in the gut lumen [56]. Thus DPP IV activity can be measured without prior cell lysis, simply by adding a specific substrate, e.g.…”