Related Experiment Video
Updated: Aug 5, 2026

Evaluation of the Interplay Between the Complement Protein C1q and Hyaluronic Acid in Promoting Cell Adhesion
Published on: June 15, 2019
Calreticulin is released from activated neutrophils and binds to C1q and mannan-binding protein
P Eggleton1, T S Lieu, E G Zappi
1Department of Pathology, Boston University School of Medicine, Massachusetts 02118.
Abstract:
The Ca2+ storage protein calreticulin is associated with the endoplasmic reticulum and shares a high degree of amino acid homology with the surface receptor C1q-R. In this study, flow cytometric analysis detected calreticulin on the neutrophil surface, which decreased during stimulation probably as a consequence of shedding, as calreticulin was found by ELISA in the cell supernatants of stimulated cells. Antibodies raised against C1q-R and calreticulin demonstrated a high degree of immunological cross-reactivity for purified calreticulin as determined by dot blot analysis. Western blots of neutrophil subcellular fractions located calreticulin in both the cytosol and cell membrane fractions; C1q-R was largely confined to the cell membrane. Calreticulin and C1q-R both bind to C1q and mannan-binding protein. Therefore, calreticulin may be shed on cell activation and may be associated with the cell membrane, where it can potentially interact with C1q and serum lectins. The implications of this are discussed.
More Related Videos
11:32Real-Time, High-Throughput Microscopic Quantification of Human Neutrophil Extracellular Trap Release and Assessing the Pharmacology of Antagonists
Published on: October 18, 2024
08:14Rapid Magnetic-microbead Method for Efficient Purification of Low-density Neutrophils
Published on: November 11, 2025
Related Concept Videos
Protein Folding Quality Check in the RER
Export of Misfolded Proteins out of the ER
Activation of Integrins
In "outside-in signaling," external factors in the extracellular space bind to exposed ligand binding sites on integrins. This causes the inactive protein to undergo a conformational change to become active. Integrins are often clustered on the cell membrane. Repetitive and regularly spaced ligand binding events provide an effective stimulus.
Selectins
Immunoglobulin-like Cell Adhesion Molecules
Ig-CAMs exhibit either homophilic binding (to other Ig-CAMs) or heterophilic binding (to other ligands such as integrins). While most Ig-CAMs...
Complement System