The metastasis‐associated molecule C4.4A promotes tissue invasion and anchorage independence by associating with the alpha6beta4 integrin

Abstract

C4.4A is a metastasis-associated molecule that functions appear to rely on associated alph6beta4 integrin. To corroborate the impact of the C4.4A-alpha6beta4 integrin association on metastasis formation, C4.4A was knocked-down in a highly metastatic rat pancreatic adenocarcinoma (ASML, ASML-C4.4Akd). Metastasis formation by ASML-C4.4Akd cells after intrafootpad application was strongly retarded in draining nodes and lung colonization was rare. Furthermore, cisplatin treatment significantly prolonged the survival time only of ASML-C4.4Akd-bearing rats. ASML-C4.4Akd cells display reduced migratory activity and impaired matrix protein degradation due to inefficient MMP14 activation; loss of drug-resistance is due to mitigated PI3K/Akt pathway activation. These losses of function rely on the laminin receptor C4.4A recruiting activated alpha6beta4 integrin into rafts, where C4.4A cooperates with alpha6beta4 and via alpha6beta4 with MMP14. Within this raft-located complex, MMP14 provokes focalized matrix degradation and mostly alpha6beta4 integrin promotes BAD phosphorylation and upregulated Bcl2 and BclXl expression. Thus, metastasis-promoting activities of C4.4A are not genuine characteristics of C4.4A. Instead, the raft-located laminin receptor C4.4A recruits alpha6beta4 integrin and supports via the alpha6beta4 integrin MMP14 activation. Thereby C4.4A acts as a linker to facilitate several steps in the metastatic cascade. Taking the restricted C4.4A expression in non-transformed tissue, this knowledge should pave the way toward the use of C4.4A as a therapeutic target.

β2-Adrenergic Signalling Promotes Cell Migration by Upregulating Expression of the Metastasis-Associated Molecule LYPD3

“…This is an interesting observation because it is thought that LYPD3 can be cleaved from the cell surface by ADAM Metallopeptidase Domain (ADAM)-10 and -17 and this shedding can be induced by hypoxia [62]. To speculate, once LYPD3 has been shed, it may still be able to bind laminin, via associating with the α6β4 integrin and matrix metallopeptidase-14 (MMP-14) and contribute towards its fragmentation and the observed decrease in LAMC1 that we observed in our proteomic analysis [60,63]. Alternatively, like its structural homologue urokinase-type plasminogen activator receptor (uPAR), shed-LYPD3 could function as a chemoattractant [64].…”

Crystal Structures of Human C4.4A Reveal the Unique Association of Ly6/uPAR/α-neurotoxin Domain

“…The functional site of C4.4A for ligand binding C4.4A was reported to interact with both α6β4 integrin and MMP14, promoting wound healing and metastasis [45]. In addition, the interaction between C4.4A with Anterior Gradient 2 (AGR2) stimulates pancreatic ductal adenocarcinoma cell aggressiveness and reduces sensitivity to chemotherapy drug gemcitabine.…”

“…We chose to focus on C4.4A (encoded by LYPD3), which contains two LU-domains followed by a mucin-type region rich in serine, threonine and proline (STP-rich region) and a C-terminal GPI-anchor [41,42]. No well-defined function has yet been assigned to C4.4A, but circumstantial evidence suggests that it could play a role in cell adhesion, migration and invasion through established interaction with laminins [43], integrins and MMP14 [44,45], and/or Anterior Gradient 2 (AGR2) [46]. Nonetheless, expression of C4.4A is strictly regulated under normal homeostatic conditions as it represents a robust biomarker for the presence of stratum spinosum in stratified squamous epithelia of the skin and for squamous differentiation of epithelia in other organs such as esophagus, vagina, oral cavity, and rectum [27,42,47].…”

Expression and crystallographic studies of the D1D2 domains of C4.4A, a homologous protein to the urokinase receptor

“…Whereas the urokinase receptor (uPAR) has three LU domains, all of which participate in the dynamic assembly of a high-affinity binding site for its primary ligand uPA, C4.4A has only two LU domains and thus resembles its close structural homologue Haldisin, which is an epithelial biomarker in the stratum granulosum (Gå rdsvoll et al, 2013). Circumstantial evidence suggests that C4.4A plays a role in adhesion, migration and invasion similar to that of uPAR (Smith et al, 2001;Thuma et al, 2013;Kriegbaum et al, 2015). However, how C4.4A interacts with its putative ligands to perform its functions and how the two LU domains are arranged remain unknown.…”