Radioimmunoprecipitation Assay buffer (Sigma-Aldrich; Merck KGaA) as well as Protease Inhibitor (Sigma-Aldrich; Merck KGaA) were used to lyse cells (28 (link)). Following protein collection, a BCA Pierce Assay (Thermo Fisher Scientific, Inc.) was used to quantify the protein concentration. Protein (50 µg) from each sample was denatured and resolved by 10% SDS-PAGE (EMD Millipore, Billerica, MA, USA) and electroblotted to a polyvinylidene fluoride (PVDF) membrane (EMD Millipore). PVDF membranes were incubated with 5% non-fat milk for one hour at room temperature and were then incubated with anti-TSPAN1 antibody (1:300; cat.no. NBP2-33867; Novus Biologicals, LLC, Littleton, CO, USA) or anti-β-actin antibody (1:1,000; cat.no. NB600-503; Novus Biologicals, LLC) at 4°C overnight. Following washing with TBS with 5% Tween-20, the membrane was incubated with horseradish peroxidase-conjugated secondary antibodies (1:3,000; cat.no. NB710-57836; Novus Biologicals, LLC) for 1.5 h at room temperature. Finally, signals were developed by enhanced chemiluminescence (Pierce; Thermo Fisher Scientific, Inc.). The optical density of each protein band was quantified by a scanning densitometer and Quantity One software (version 4.4.1; Bio-Rad Laboratories, Inc., Hercules, CA, USA). Each lane of protein band density was normalized against corresponding β-actin densities.