Plasmin mediated cleavage of C3 is enhanced by Sbi and Efb.

<p>(A) In the presence of Sbi and Efb (lane 1 and 2) the C3 α-chain decreased and C3 cleavage products (indicated by arrows) appeared. CRASP-5 did not show this effect. C3 was incubated with SAK-activated plasmin (PL_SAK) in the presence of Sbi, Efb, CRASP-5, or HSA. Samples were separated by SDS-PAGE and C3 cleavage products were visualized using Western blot analysis. (B) A similar assay was performed with uPa as activator and this time the fragments Sbi 1–2, Sbi 3–4, and Efb-C were assayed. Sbi 3–4 (lane 5 and 6) and Efb-C (lane 8 and 9) enhanced the plasmin mediated C3 cleavage as seen by the appearance of small cleavage products. The IgG-binding Sbi 1–2 (mobility of 17 kDa) did not affect the C3 cleavage pattern (lane 2 and 3). Polyclonal C3 antiserum was used for detection. (C) In the presence of Sbi 3–4 and Efb-C the plasmin mediated C3 proteolysis was enhanced as measured by ELISA. C3 was immobilized and plasmin (activated by uPa or SAK) together with Sbi 3–4 or Efb-C were added. C3 deposition was detected after 3 h with C3a antiserum. CRASP-5 and HSA did not influence plasmin cleavage of C3. (D) Sbi 3–4 and Efb-C significantly enhanced C3 degradation by plasmin in a dose dependent manner. The C3 amount after incubation with plasmin was set to 100%. Data in C and D are mean values of three independent experiments; error bars indicate standard deviations. *<i>p</i><0.05; **<i>p</i><0.01 and ***<i>p</i><0.001.