Ly6 family member C4.4A binds laminins 1 and 5, associates with galectin‐3 and supports cell migration

Abstract

C4.4A is a member of the Ly6 family, with low homology to uPAR. It has been detected mainly on metastasizing carcinoma cells and proposed to be involved in wound healing. So far, C4.4A has been observed as an orphan receptor, and its functional activity has not been explored. Using recombinant rat C4.4A (rrC4.4A) made in a eukaryotic expression system, we demonstrate by immunohistology that C4.4A ligands are strongly expressed in tissues adjacent to squamous epithelia of, e.g., tongue and esophagus, the expression pattern partly overlapping with laminin (LN) and complementing the C4.4A expression that is found predominantly on the basal layers of squamous epithelium. ELISA screening of several components of the extracellular matrix revealed selective binding of rrC4.4A to LN1 and LN5 and that transfection of the BSp73AS tumor line with C4.4A cDNA (BSp73AS-1B1) promoted LN1 and LN5 binding. Binding of BSp73AS-1B1 to LN5 and, less markedly, LN1 induced spreading, lamellipodia formation and migration. C4.4A also associates with galectin-3 in nontransformed tissues and tumor lines. There is evidence that the association of C4.4A with galectin-3 influences LN adhesion. C4.4A was described originally as a metastasis-associated molecule. Our findings that LN1 and LN5 are C4.4A ligands, that galectin-3 associates with C4.4A and that C4.4A ligand binding confers a migratory phenotype are well in line with the supposed metastasis association. ' 2005 Wiley-Liss, Inc.Key words: C4.4A; laminin; galectin; cell migration LNs are adhesive glycoproteins found in the basement membrane. Fifteen LN isoforms have been identified. 1 LN isoforms are tissue-specific and expressed in a developmentally regulated pattern. 2,3 Cell adhesion to LN plays an important role in maintaining normal tissue organization. LNs promote cell adhesion and migration, 4 are involved in the control of cell proliferation and gene expression 5 and stimulate neurite outgrowth, 6 the multitude of functions being brought about by a large array of receptors. 7 The most prominent LN receptors are integrins, but distinct receptors have also been described, e.g., a-dystroglycan, syndecans, the 67 kDa LN receptor and galectins. 7,8 a-Dystroglycan provides a link between the basement membrane and the dystrophin-actin cytoskeleton. 9 Its binding to LN is Ca 2þ -dependent 10 and requires carbohydrate moieties. 11 Binding of syndecans 2 and 4 to LN5 induces expression of MMP-1. 12 Moreover, syndecan 1 interacts with unprocessed LN5 in migrating keratinocytes, and this interaction depends on the presence of the glycosaminoglycan chain. 13 Galectins belong to the family of galactose-specific lectins and bind the lactosamine-type sugars on LN1. 8 However, at high concentrations, galectins 3 and 1 can downregulate adhesion to LN, probably by blocking the cellular attachment sites. 14,15 The 67 kDa LN receptor can act in concert with a6b4 to promote cell adhesion to LN1. 16 It is also involved in the degradation of LN1 and the release of motility fragments. 17 The GPI-ancho...

N-Glycosylation of Laminin-332 Regulates Its Biological Functions

“…These data suggest that GnT-V affects the cancer by promoting cell motility and changing the stability for growth factor receptors at the cell surface. Ly6 family member C4.4A can bind to Lm332, and its association of galectin-3 influences Lm332 adhesion (37). In addition, galectin-3-dependent oligomerization potentiates NG2-mediated activation of ␣3␤1 integrin (38).…”

Altered LKB1/CREB-regulated transcription co-activator (CRTC) signaling axis promotes esophageal cancer cell migration and invasion

“…LYPD3 is upregulated in metastasizing tumor cells, but showed restricted expression in normal adult tissues (Rosel et al, 1998;Seiter et al, 2001;Wurfel et al, 2001;Hansen et al, 2008). The exact biochemical functions of LYPD3 are unknown; however, it was shown to interact with the adhesion proteins laminin-1, laminin-5 and galectin-3, which might promote metastasis and matrix invasion (Paret et al, 2005). With regard to esophageal cancer, LYPD3 was proposed as a histological marker of invasion and metastasis for ESCC (Hansen et al, 2008).…”

Expression of C4.4A, a Structural uPAR Homolog, Reflects Squamous Epithelial Differentiation in the Adult Mouse and during Embryogenesis

“…Although these data clearly highlight C4.4A as a promising biomarker for poor prognosis in this group of lung cancer patients, a causal relationship responsible for this correlation is not evident, given that a well-defined biochemical function has so far not been assigned to C4.4A. Nevertheless, circumstantial evidence has prompted the speculations that C4.4A may be involved in either cell-matrix interactions (Paret et al 2005;Rösel et al 1998;Smith et al 2001) or in cell-cell adhesion .…”