TSHR cleavage is not induced by MS-1. CHO-hTSHR cells were treated with 100 μU/ml of TSH for 24 hours and stained with two monoclonal TSHR-Ab’s, and showed a reduction in the immunoreactivity of RSR-4 (a) but not RSR-1 (b). In contrast, similar treatment with MS-1 (5 μg/ml) did not alter immunoreactivity by either RSR-4 (c) or RSR-1 (d), indicating that MS-1 did not accelerate TSHR cleavage. The thin lines indicate staining of CHO-hTSHR cells without TSH (a and b) or MS-1 (c and d), and thick lines indicate CHO-hTSHR cells with TSH (a and b) and MS-1 (c and d), respectively.