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Characterization of C1q, C1s and C-1 Inh synthesized by stimulated human monocytes in vitro
Insights
Human monocytes synthesize complement components C1q, C1s, and C1 inhibitor (C1 Inh). Their structures and molecular weights are characterized, revealing similarities to plasma-derived proteins, with some differences in C1 Inh.
Area of Science:
- Immunology
- Molecular Biology
- Biochemistry
Background:
- The complement system is crucial for innate and adaptive immunity.
- Monocytes are key immune cells involved in complement production.
- Understanding complement component synthesis by monocytes is vital for immunology research.
Purpose of the Study:
- To characterize complement components C1q, C1s, and C1 inhibitor synthesized by human monocytes.
- To compare monocyte-derived complement proteins with their plasma counterparts.
- To investigate the effect of monensin on the synthesis and glycosylation of these proteins.
Main Methods:
- Human monocytes were cultured and stimulated.
- Synthesized complement components C1q, C1s, and C1 Inh were analyzed using SDS-PAGE.
- Monensin treatment was employed to study intracytoplasmic accumulation and glycosylation.
Main Results:
- C1q comprises three chains (A, B, C) forming A-B and C-C subunits, identical to plasma C1q.
- C1s is secreted as a non-activated, single-chain protein (Mr ~87,000), similar to plasma proenzymic C1s.
- Secreted C1 Inh (Mr ~100,000) showed a slightly higher molecular weight than plasma C1 Inh; monensin treatment led to intracytoplasmic accumulation at various glycosylation stages.
Conclusions:
- Human monocytes synthesize and secrete complement components C1q, C1s, and C1 Inh.
- The characterized monocyte-derived proteins are largely identical to plasma-derived forms, with notable differences in C1 Inh molecular weight.
- Monensin treatment highlights the role of glycosylation in the processing and secretion of these complement proteins by monocytes.
Abstract:
C1q, C1s and C1 Inh synthesized and secreted by human monocytes were characterized by SDS-PAGE. C1q is formed of three chains A (Mr approximately 35 000), B (Mr approximately 33 000) and C (Mr approximately 25 000) which are associated in two subunits A-B and C-C. It appears identical to C1q purified from plasma. C1s is secreted as a non-activated, monocatenar protein of Mr approximately 87 000 identical to proenzymic C1s from plasma. Secreted C1 Inh (Mr approximately 100 000) has a slightly higher Mr than purified plasmatic C1 Inh. Monensin treatment of the cells favours the intracytoplasmic accumulation of products at various glycosylation stages.