Deletion of the latent matrix protease site eliminates processing, but does not affect oligomerization of MATN1ΔA2. A. Schematic diagram of Construct 1: MATN1ΔA2; and Construct 2: MATN1ΔA2Del. B. Western blot analysis of conditioned medium of Cos cells transfected with Construct 1 or 2 under the same experimental conditions as described above. C. Proteolytic cleavage of MATN1ΔA2Del is inhibited by matrix protease inhibitors EDTA and actinonin. Cos cells transfected with MATN1ΔA2Del were incubated with EDTA and actinonin at indicated concentrations for 48 hours in the presence or absence of 1% FBS. Conditioned medium was collected for western blot analysis under reducing conditions using antiserum against the FLAG tag.