ATG4B and temporal arteritis: To provide further evidence that Am-F4a decreased the viability of GCa cells via inhibiting ATG4B activity, we used ATG4B siRNA approach to specifically silence ATG4B expression, results revealed that the effect of Am-F4a on GCa cell growth and apoptosis was obviously attenuated in ATG4B siRNA treated cells compared to control cells (Fig. 4f and Fig. S6).