Extracellular calumenin suppresses ERK1/2 signaling and cell migration by protecting fibulin-1 from MMP-13-mediated proteolysis

Abstract

Extracellular proteins are vital for cell activities, such as cell migration. Calumenin is highly conserved among eukaryotes, but its functions are largely unclear. Here, we identify extracellular calumenin as a suppressor of cell migration and tumor metastasis. Calumenin binds to and stabilizes fibulin-1, leading to inactivation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) signaling. We further identify the minimal functional domain of calumenin (amino acids 74-138 and 214-280). Depletion of calumenin induces fibulin-1- and phospho-ERK1/2 (pERK1/2)-dependent promotion of cell migration. Consistently, in hepatocellular and pancreatic carcinoma, both calumenin and fibulin-1 are downregulated. Furthermore, we show that matrix metalloproteinase-13 (MMP-13) proteolyzes fibulin-1 and that calumenin protects fibulin-1 from cleavage by MMP-13. Calumenin, together with fibulin-1, also interacts with fibronectin and depends on both syndecan-4 and α5β1-integrin to suppress ERK1/2 signaling and inhibit cell migration. Thus, extracellular calumenin regulates fibulin-1 to have crucial roles in ERK1/2 signaling and cell migration.

Calumenin and fibulin-1 on tumor metastasis: Implications for pharmacology

“…However, the role of fibulin-1 in cancer is still elusive. Both Fibulin-1 mRNA and protein levels are down-regulated in prostate cancer [47], gastric cancer [48], hepatocellular carcinoma [6,49], renal cell carcinoma [50], bladder cancer [51], and pancreatic carcinoma [6]. The down-regulation seems to be achieved by promoter hypermethylation of FBLN1 gene [48,49,51].…”

“…Cab45S also interacts with SERCA2b and promotes cell proliferation in a Ca 2+ -dependent manner [60]. The expression level of RCN1 and Cab45 is commonly up-regulated in cancer tissues, suggesting a relationship between them and cancer [6,56,60].…”

“…Although in vitro test shows that fibulin-1 does not perturb fibronectin-integrin-␣5␤1 binding [17], a recent report indicates that fibulin-1 inhibits cell migration in an integrin-␣5␤1-dependent manner with unknown mechanism [6]. Fibronectin is commonly proteolyzed by MMPs [20], and the resulted fibronectin fragments, such as those containing the integrin ligand Arg-GlyAsp (RGD) domain, are able to modulate various cellular processes including integrin-mediated signaling [21][22][23][24].…”

“…The CREC family proteins show various localization including the nucleus, cytosol, endoplasmic reticulum (ER), Golgi apparatus, cell membrane, as well as extracellular space, and participate in a large variety of physiological processes [56]. Their complex localizations result in various functions, like chaperone activity [57], calcium homeostasis [58], secretory cargo sorting [59], cell proliferation [60], and cell migration [6]. Notably, an isoform of Cab45, Cab45S is reported to inhibit ER-stress induced apoptosis via GRP78, thus promotes tumor progression [61].…”

“…Some extracellular proteases, such as matrix metalloproteinases (MMPs), are able to process ECM into the functional fragment derivatives and to module cell migration [5]. Calumenin and fibulin-1 are two reported ECM proteins that cooperatively and efficiently inhibit cell migration and tumor metastasis [6], and we proposed that they could be considered as targets for anti-metastasis therapy. In this review, we focus on the functions of these two proteins and the mechanisms by which they regulate cell migration and tumor metastasis.…”