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Mitigation of Blood Borne Cell Attachment to Metal Implants through CD47-Derived Peptide Immobilization
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Complement inhibitor membrane cofactor protein (MCP; CD46) is constitutively shed from cancer cell membranes in

Juha Hakulinen1, Sami Junnikkala, Timo Sorsa

  • 1Department of Bacteriology and Immunology, Haartman Institute, University of Helsinki, and Helsinki University Central Hospital (HUCH), Helsinki, Finland. Juha.Hakulinen@helsinki.fi

European Journal of Immunology
|August 13, 2004
PubMed

Insights

Human cell-surface protein CD46, crucial for immune regulation, can be released from tumor cells in functional forms. This shedding, mediated by metalloproteinases, occurs on vesicles or as soluble protein, extending CD46

Area of Science:

  • Immunology
  • Cell Biology
  • Biochemistry

Background:

  • CD46 is a human cell-surface protein involved in complement protection, immune regulation, and microbial receptor functions.
  • Alternative splicing of CD46 mRNA generates multiple isoforms with varying molecular weights, affecting the serine/threonine/proline-rich region or cytoplasmic tail.
  • CD46's role extends beyond cell membranes, but its release mechanisms and functional implications in soluble or vesicular forms were not fully understood.

Purpose of the Study:

  • To investigate the proteolytic modification and release of CD46 from tumor cell membranes.
  • To characterize the forms of CD46 liberated into the cell culture medium.
  • To determine the functional activity of released CD46 and factors influencing its shedding.

Main Methods:

  • Analysis of CD46 released from tumor cells into cell culture medium.
  • Characterization of vesicular and soluble CD46 forms using biophysical techniques.
  • Inhibition studies using selective metalloproteinase inhibitors.
  • Assessment of CD46 functional activity in C3b cleavage.

Main Results:

  • Tumor cells released intact CD46 (60-65 kDa) on 200 nm vesicles and soluble CD46 (55-60 kDa) lacking transmembrane domains.
  • CD46 release is mediated by metalloproteinase cleavage, enhanced by hydrogen peroxide exposure or cell detachment.
  • Both vesicular and soluble CD46 retained functional activity, promoting C3b cleavage by factor I.

Conclusions:

  • CD46 can be proteolytically cleaved and released from tumor cell membranes in functional vesicular and soluble forms.
  • Metalloproteinases play a key role in CD46 shedding, which is influenced by cellular stress and matrix interactions.
  • The functional activity of CD46 is not limited to the cell surface, with implications for immune modulation in the tumor microenvironment.

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