Polysialic acid controls NCAM signals at cell–cell contacts to regulate focal adhesion independent from FGF receptor activity

Abstract

SummaryThe polysialic acid (polySia) modification of the neural cell adhesion molecule NCAM is a key regulator of cell migration. Yet its role in NCAM-dependent or NCAM-independent modulation of motility and cell-matrix adhesion is largely unresolved. Here, we demonstrate that loss of polySia attenuates tumour cell migration and augments the number of focal adhesions in a cell-cell contact-and NCAM-dependent manner. In the presence or absence of polySia, NCAM never colocalised with focal adhesions but was enriched at cell-cell contacts. Focal adhesion of polySia-and NCAM-negative cells was enhanced by incubation with soluble NCAM or by removing polySia from heterotypic contacts with polySia-NCAM-positive cells. Focal adhesion was compromised by the src-family kinase inhibitor PP2, whereas loss of polySia or exposure to NCAM promoted the association of p59Fyn with the focal adhesion scaffolding protein paxillin. Unlike other NCAM responses, NCAM-induced focal adhesion was not prevented by inhibiting FGF receptor activity and could be evoked by NCAM fragments comprising immunoglobulin domains three and four but not by the NCAM fibronectin domains alone or by an NCAM-derived peptide known to interact with and activate FGF receptors. Together, these data indicate that polySia regulates cell motility through NCAM-induced but FGF-receptor-independent signalling to focal adhesions.

A ZIP6-ZIP10 heteromer controls NCAM1 phosphorylation and integration into focal adhesion complexes during epithelial-to-mesenchymal transition

“…This discovery triggered a 2 nd set of interactome analyses, which first produced an in-depth analysis of the molecular environment of NCAM1 in the same cell model and, next, explored how the knockout of ZIP6 affects NCAM1 interactions. The study established prominent interactions of NCAM1 with integrins that are modulated by ZIP6, thereby corroborating observations by others, which had previously documented that NCAM1 (i) either associates directly with focal adhesion complexes during EMT in the NMuMG model23, or (ii) induced focal adhesions in a cell-cell contact dependent manner in a human neuroblastoma cell model24. We documented that ZIP6—like its PrP cousin—promotes an increase in steady-state NCAM1 levels during EMT but—unlike PrP—serves to limit NCAM1 polysialylation that occurs during the execution of this morphogenetic program.…”

NCAM1 Polysialylation

“…Whereas the aforementioned study did not address the possible role of polySia in this paradigm, a related manuscript suggests that its presence may be a critical factor that determines the balance between cell-cell and cell-matrix adhesion and modulates cell migration. Thus, in a neuroblastoma tumor cell migration paradigm, the loss of polySia at sites of cell-cell contacts has been observed to translate into increased focal adhesion and attenuated cell migration (Eggers et al, 2011). …”

“…In some mammalian cancer paradigms, unpolysialylated NCAM1 might be sufficient and indispensable for a lipid-raft centered signaling program that coordinates the concomitant disassembly of E-cadherin-based adherence junctions and formation of focal adhesions as a prelude to cellular movement (Frame and Inman, 2008; Lehembre et al, 2008). In contrast to invertebrates, which do not synthesize polySia-like structures and control the cell surface presentation of NCAM orthologues by internalization and proteolytic degradation (Schuster et al, 1996; Bailey et al, 1997), the possibility to steer NCAM1 interactions by means of polysialylation provides vertebrates with an additional level of regulation, and the ratio between unpolysialylated and polysialylated NCAM1 seems to be critical for balancing cell-cell and cell-matrix adhesion as a prerequisite for the morphogenetic events during migration and differentiation (Seidenfaden et al, 2006; Eggers et al, 2011). …”

Determination of major sialylated N-glycans and identification of branched sialylated N-glycans that dynamically change their content during development in the mouse cerebral cortex

“…In the rodent brain, 40 % of total N-glycan is sialylated and approximately 10 % of these N-glycans carry polysialic acids (PSA), which are partly comprised of PSA on neural cell adhesion molecules (N-CAM) [8]. Growing evidence suggests that structures containing sialic acid play particularly important roles in cell-cell and extracellular matrix interactions [9–12]. Proteins that recognize and bind to a certain structure of sugar chains are called lectins.…”