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Expression and characterization of membrane co-factor protein (MCP) in human skin
K Sayama1, S Shiraishi, Y Shirakata
1Department of Dermatology, University of Ehime School of Medicine, Japan.
Abstract:
Membrane co-factor protein (MCP; CD46) is an integral membrane protein with molecular weight (MW) of the two species of 63 kD and 55 kD, and regulates autologous complement activation, with the activity of factor I cofactor. The quantity of each species is genetically regulated, and two codominantly inherited allelic variants account for the three phenotypic patterns. By immunohistochemical study, MCP was found both in the intercellular spaces of the epidermis and on the endothelial cells in the dermis of normal human skin in vivo. The intensity of the staining pattern was higher in the basal layer than in the granular layer. By Western blot analysis with use of a monoclonal antibody, MCP in the epidermis appeared as several bands ranged from 60-50 kD, with a major band of 56 kD, which was different from those in either polymorphonuclear cells, platelets, and cultured keratinocytes. No other variants were found in the epidermis obtained from skin of 20 normal humans. Complement activation in human skin may be regulated at several steps, including DAF and HRF20, thereby protecting cells from autologous complement attack.
Insights
Membrane cofactor protein (MCP; CD46) regulates complement activation in human skin. This study identified MCP in skin epidermis and dermis, revealing its role in protecting skin cells from complement attack.
Area of Science:
- Immunology
- Dermatology
- Cell Biology
Background:
- Membrane cofactor protein (MCP; CD46) is an integral membrane protein crucial for regulating autologous complement activation.
- MCP exhibits cofactor activity for factor I, playing a key role in immune regulation.
- Genetic regulation of MCP quantity and allelic variants influence phenotypic patterns.
Purpose of the Study:
- To investigate the presence and distribution of MCP in normal human skin.
- To characterize the molecular weight and variants of MCP in the epidermis.
- To understand the role of MCP in regulating complement activation within the skin.
Main Methods:
- Immunohistochemical analysis of normal human skin.
- Western blot analysis of epidermal extracts using a monoclonal antibody against MCP.
- Examination of skin samples from 20 healthy individuals.
Main Results:
- MCP was detected in both the intercellular spaces of the epidermis and on endothelial cells in the dermis.
- Staining intensity for MCP was notably higher in the basal layer compared to the granular layer of the epidermis.
- Western blot analysis revealed MCP in the epidermis as multiple bands (60-50 kD), with a predominant 56 kD band, distinct from other cell types.
Conclusions:
- MCP is present in normal human skin, with specific distribution patterns in the epidermis and dermis.
- The identified MCP variants in the epidermis are consistent across individuals, suggesting a conserved role.
- MCP, alongside other complement regulatory proteins like DAF and HRF20, contributes to protecting skin cells from autologous complement-mediated damage.