Abstract 1643: Physical and functional interactions between acid sensing ion channel 1 (ASIC1) and integrin β1 in glioma cells.

Abstract The local microenvironment of a cancer cell plays important roles in tumor metastasis. Major components of this local niche are ion channels, integrin receptors, and the extracellular matrix. Glioma cells express a specific amiloride-sensitive and constitutively active non-selective cation channel composed of ASIC1, α- and gENaC subunits, members of the Deg/ENaC superfamily of non-voltage gated sodium channels. Inhibition of this channel is associated with reduced migration and proliferation of the glioma cell. As gliomas are highly invasive, we hypothesized that channel activity was engaging an intracellular signaling pathway regulating migration and proliferation by interacting with integrin β1. We have shown the physical proximity of the ASIC1 subunit and integrin β1 by co-immunoprecipitation in D54MG glioma cells. A functional interaction between these two proteins was demonstrated when we found that stable (shRNA) knock-down of integrin β1 attenuated the amiloride-sensitive current by 89±24% (n≥9; ±SD P<0.001). Furthermore, prolonged (24h) inhibition of this glioma channel by PcTX-1, a specific ASIC1 inhibitor, down-regulated integrin β1 expression (by 60% ± 12% (SD) n≥3 P<0.001). The surface expression of ASIC1 in glioma cells is also regulated by integrin β1. Using biotinylation, we found that stably knocking down integrin β1 inhibited the surface expression of ASIC1. In contrast, up-regulating membrane expression of integrin β1 by coating dishes with either fibronectin or vitronectin, increased the surface expression of ASIC1. This effect was not observed when dishes were coated with poly-L-lysine. We have previously shown that knockdown of ASIC1 reduced the phosphorylation level of ERK1/2, a key mediator of tumor cell proliferation and migration (Rooj et al. J. Biol. Chem. 287:4053, 2012). In the present study, phosphorylation of ERK1/2 was also reduced by knockdown of integrin β1 (by 58% ± 20% (SD) n≥3 P<0.001). Our data reveal a novel interaction between ASIC1 and integrin β1 in the regulation of the MAPK pathway that may form a mechanism by which changes in Na+ current can modulate cell proliferation and migration. Citation Format: Arun K. Rooj, Carmel M. McNicholas, Catherine M. Fuller. Physical and functional interactions between acid sensing ion channel 1 (ASIC1) and integrin β1 in glioma cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1643. doi:10.1158/1538-7445.AM2013-1643