Effect of laminin‐1 on intestinal cell differentiation involves inhibition of nuclear nucleolin

Abstract

Intestinal epithelial cells are characterized by continuous renewal and differentiation events, which may be influenced by the basement membrane, and in particular laminins, which are major components of this specialized extracellular matrix. The function and signaling pathways of laminins in these processes are still poorly documented. In this study, we investigated the possible role and the subcellular localization of nucleolin, a nuclear shuttling protein, in relation to differentiation of human intestinal epithelial Caco2/TC7 cells triggered by exogenous laminin-1. Immunofluorescence and Western blot analysis indicated that laminin-1 induced early differentiation of the cells concomitantly to a decrease in nuclear nucleolin and its a cell surface location. We also showed that both effects of laminin-1 on Caco2/TC7 cells--induction of the differentiation marker sucrase-isomaltase and redistribution of nucleolin--could be mediated by a beta1-integrin dependent cascade that implicated activation of the p38 MAPK pathway. In addition, knock-down of nucleolin expression by the small interfering RNA strategy mimicked the effect of laminin-1 as it resulted in the induction of cell polarization and differentiation. Thus, our study suggests that changes in the subcellular distribution and expression level of nucleolin play an important role in intestinal cell differentiation and relay the signaling pathway induced by laminin-1.

In vitro models of intestinal epithelial cell differentiation

“…Knockdown of nucleolin expression by the small interfering RNA strategy mimicked the effect of laminin-1 as it resulted in the induction of cell polarization and differentiation. It was also shown that both effects of laminin-1 on Caco-2/TC7 cells, induction of sucrase and loss of nuclear nucleolin, are mediated by a β1-integrin dependent cascade that implicates activation of the p38 MAPK pathway (Turck et al, 2006 and Figure 5). …”

“…(B) Nucleolin inhibition induces differentiation of Caco-2/TC7 cells: a small interfering RNA strategy, used to knock down nucleolin expression, leads to a clear induction of the morphological polarization of the cells (arrows point to the brush border membrane) and of sucrase as compared to control cells such as Caco-2 cells cultured on laminin-1 (not illustrated). The scheme summarizes data obtained by Turck et al (2005Turck et al ( , 2006 showing that the β1-integrin-mediated adhesion of cells to laminin-1 leads to signal transduction that implicates the p38 MAP kinase and to the modulation of differentiation gene expression via loss of nucleolin and induction of Cdx2.…”

Nucleolin functions in nucleolus formation and chromosome congression

“…Nucleolin plays essential roles in rDNA transcription, rRNA maturation, ribosome assembly and nucleocytoplasmic transport (Ginisty et al, 1999;Srivastava and Pollard, 1999). As a multifunctional protein, nucleolin has also been proposed to be a nuclear matrix-binding protein (Gotzmann et al, 1997), to interact with telomerase (Khurts et al, 2004) and to be involved in the regulation of apoptosis (Mi et al, 2003), intestinal cell differentiation (Turck et al, 2006) and remodeling of nucleosomes (Angelov et al, 2006). Although many functions of nucleolin have been clarified, previous studies have fallen short of demonstrating its functions during mitosis.…”

A Simple Approach to Cancer Therapy Afforded by Multivalent Pseudopeptides That Target Cell-Surface Nucleoproteins

“…In addition, molecules such as urokinase, which are involved in mechanisms regulating pericellular proteolysis and cellsurface adhesion mitogenesis, bind and are cointernalized along with cell-surface nucleolin (9,10). Other cell-surface nucleolin binding proteins, such as laminin-1, factor J, and L-and P-selectins, are involved in cell differentiation, cell adhesion regulation, leukocyte trafficking, inflammation, and angiogenesis (11)(12)(13)(14). Cell-surface nucleolin has been validated as a novel target for anticancer therapy by using several molecules such as endostatin, the AS1411 aptamer, acharan sulfate, the F3 tumor-homing peptide coupled to radioactive isotopes (15)(16)(17), and the HB-19 pseudopeptide (18).…”