Hepatocyte Growth Factor-induced Ectodomain Shedding of Cell Adhesion Molecule L1

Abstract

The L1 cell adhesion molecule and its soluble form are tumor-associated proteins and potential markers for tumor staging as well as targets for therapeutic intervention. Soluble L1 is produced by metalloprotease-mediated ectodomain shedding of L1. We investigated effects of hepatocyte growth factor (HGF), a growth factor shown to increase invasiveness of renal carcinoma cells, on ectodomain shedding of L1 from these cells. All of the tested L1-positive renal carcinoma cell lines released a 180-kDa form of L1 into the medium. In the presence of serum, addition of HGF led to a dose-dependent increase in L1 shedding with a maximum reached at 5 ng/ml. In contrast, L1 shedding was inhibited by glial cell linederived neurotrophic factor (GDNF). The tyrosine kinase inhibitor Genistein reduced basal and HGFstimulated L1 shedding, indicating that protein phosphorylation is involved. To investigate the role of the L1 intracellular domain, two mutants of the L1 cytoplasmic part were constructed. L1trun lacking the complete intracellular domain showed enhanced basal shedding. In a L1YH mutant, containing the mutation tyrosine 1229 to histidine that deletes the ankyrin binding motif of L1, basal shedding was reduced. Disruption of actin assembly by cytochalasin D also reduced shedding of L1. These results indicate that the cytoplasmic domain regulates basal shedding of L1, and association with the cytoskeleton through the L1 ankyrin binding site is involved. HGF stimulated L1 shedding in both mutants, indicating that receptor-mediated phosphorylation in the L1 cytoplasmic domain is not required for HGF-stimulated shedding.The L1 cell adhesion molecule (L1) 1 was originally described as a protein of the nervous system, and mutated forms of L1 are linked to severe neurological pathologies referred to as MASA syndrome (1). A non-neuronal isoform of L1 lacking exons 2 and 27 is expressed at low levels in the normal adult human kidney (2) as well as during renal development (3). In contrast, high expression of L1 was found in 8 of 12 renal tumor cell lines and in some renal tumors (2). 2 It was shown that the cell-bound form of L1 can serve as a target for radioimmunodiagnosis of metastatic neuroblastoma (4), and L1 may also be a marker and therapeutic target for certain renal cancers.In cultured cell lines originating from a number of different tumors the L1 ectodomain was found to be cleaved proximal to the cell membrane by metalloproteases, followed by release of soluble L1 into the medium (5-7). Ectodomain shedding of L1 could be stimulated by phorbol esters and vanadate, indicating that phosphorylation events regulate L1 release (6). In cell culture soluble L1 substrate was found to stimulate cellular motility and migration (8). Release of soluble L1 is not restricted to cells in culture as soluble L1 was recently detected in serum samples of patients with ovarian and uterine tumors and is believed to lead to increased cell migration and metastatic spread in these malignancies (9).Here we investigated whether hepatocyte grow...

Ligand-of-Numb protein X is an endocytic scaffold for junctional adhesion molecule 4

“…Hepatocyte growth factor regulates cell motility and triggers the remodeling of cell junctions (Pollack et al, 2004). Under the treatment of HGF, the surface expression of cell adhesion proteins alters through shedding and endocytosis (Kamei et al, 1999;Tanaka et al, 2002;Heiz et al, 2004). Transforming growth factor b , which is also a well-established inducer of EMT, downregulates the expression of E-cadherin and increases the expression of N-cadherin (Miettinen et al, 1994;Zavadil and Bo¨ttinger, 2005).…”

Metastasis: cell-autonomous mechanisms versus contributions by the tumor microenvironment

“…Similar to its function in neurons, NCAM also modulates cell-matrix adhesion of tumor cells by binding to FGFR and inducing a variety of signaling pathways that lead to b 1 integrin-mediated cell-matrix adhesion and neurite outgrowth [34]. While L1 exerts functions similar to NCAM in neurons, L1 is specifically expressed at the invasive front of gliomas, melanomas, lung, prostate, renal, ovarian and endometrial carcinoma, and its expression appears to correlate with metastasis [54][55][56][57][58][59]. Similar to NCAM, L1 has been shown to enhance migration and invasion of tumor cells in vitro.…”

Cleavage of L1 in Exosomes and Apoptotic Membrane Vesicles Released from Ovarian Carcinoma Cells

“…We showed before that shedding of L1 can be induced through stimuli like phorbol 12-myristate 13-acetate, pervanadate, and methyl-h-cyclodextrin (10,11,24). A recent study has shown that in renal carcinoma the shedding of L1 is enhanced by hepatocyte growth factor (8). Other physiologic stimuli that lead to enhanced L1 shedding have not been identified yet.…”

“…L1 plays a crucial role in axon guidance and cell migration in the developing nervous system (2,3). L1 is not only expressed in the nervous system but is also found on different tumor cells like lung cancer (4), gliomas (5), melanomas (6,7), and renal carcinoma (8). We recently reported that L1 is overexpressed in ovarian and endometrial carcinomas in a stage-dependent manner and that L1 expression was a predictor of poor outcome (9).…”