Differentiation of human colon adenocarcinoma cells alters the expression and intracellular localization of annexins A1, A2, and A5.

Butyrate induces differentiation and alters cell proliferation in intestinal-epithelial cells by modulation of the expression of several genes. Annexins are a superfamily of ubiquitous proteins characterized by their calcium-dependent ability to bind to biological membranes; their involvement in several physiological processes, such as membrane trafficking, calcium signaling, cell motility, proliferation, and differentiation has been proposed. Thus, we have analyzed changes in annexin A1 (AnxA1), annexin A2 (AnxA2), and annexin A5 (AnxA5) levels and localization in human colon adenocarcinoma cells differentiated by butyrate treatment or by culture in glucose-free inosine-containing medium. The acquired differentiated phenotype increased dipeptidyl peptidase-IV (DPP-IV) expression and alkaline phosphatase (ALP) activity, two well known brush border markers. Butyrate induces cell differentiation and growth arrest in BCS-TC2, BCS-TC2.2, HT-29, and Caco-2 cells, increasing the levels of AnxA1 and AnxA5, whereas AnxA2 decreases except in Caco-2 cells. Inosine-differentiated cells present increased amounts of the three studied annexins, as occurs in spontaneously differentiated Caco-2 cells. AnxA2 down-regulation is not due to proteasome activation and seems to be related to the butyrate-induced cell proliferation arrest; AnxA1 and AnxA5 expression is growth-state independent. AnxA1 and AnxA5 are mainly found in the cytoplasm while AnxA2 is localized underneath the plasma membrane in cell-to-cell contacts. Butyrate induces changes in subcellular localization towards a vesicle-associated pattern. Human colon adenocarcinoma cell differentiation is associated with an up-regulation of AnxA1, AnxA2, and AnxA5 and with a subcellular relocation of these proteins. No correlation between annexin levels and tumorigenicity was found. Up-regulation of AnxA1 could contribute to the reported anti-inflammatory effects of butyrate in colon inflammatory diseases.