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Catfish thrombocytes express an integrin-like CD41/CD61 complex
B J Passer1, C H Chen, N W Miller
1Department of Microbiology, University of Alabama at Birmingham, 35294, USA.
Insights
Researchers identified a specific antigen on catfish thrombocytes using monoclonal antibodies. This antigen, homologous to the human CD41/CD61 complex, plays a role in thrombocyte aggregation and shape change.
Area of Science:
- Immunology
- Comparative Biology
- Molecular Biology
Background:
- Thrombocytes (platelets) are crucial for hemostasis in vertebrates.
- The CD41/CD61 complex, composed of alphaIIb and beta3 integrin subunits, is a key platelet surface glycoprotein in mammals.
- Understanding the conservation of this complex in non-mammalian vertebrates provides insights into its evolutionary history.
Purpose of the Study:
- To identify and characterize a thrombocyte-specific antigen in catfish (Ictalurus punctatus and Ictalurus furcatus).
- To investigate the molecular composition and functional properties of this antigen.
- To determine if this antigen represents a conserved homolog of the mammalian CD41/CD61 complex.
Main Methods:
- Monoclonal antibodies (4-20 and 7-2) were used to immunoprecipitate the target antigen from catfish thrombocytes.
- Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) under reducing and non-reducing conditions was employed to analyze the glycoprotein chains.
- N-terminal amino acid sequencing was performed to identify homologous protein subunits.
- Functional assays were conducted to assess the antibodies' effect on thrombocyte aggregation and cell shape.
Main Results:
- A thrombocyte-specific antigen was identified in two catfish species.
- The antigen consists of two noncovalently associated glycoprotein chains (Mr 180,000 and Mr 95,000).
- Under reducing conditions, the Mr 180,000 chain dissociates into Mr 150,000 and 32,000 subcomponents.
- N-terminal sequencing revealed homology of the Mr 95,000 chain with beta3 integrin and the Mr 150,000 chain with alphaIIb integrin.
- The specific antibodies induced catfish thrombocyte aggregation and altered cell shape.
Conclusions:
- The identified catfish thrombocyte antigen is homologous to the alphaIIb/beta3 integrin complex, also known as the CD41/CD61 complex in mammals.
- This study provides evidence for the evolutionary conservation of the CD41/CD61 complex in bony fish.
- The findings highlight the conserved role of this complex in thrombocyte function across diverse vertebrate species.
Abstract:
A thrombocyte-specific antigen was identified in two closely related catfish, Ictalurus punctatus and Ictalurus furcatus, by monoclonal antibodies 4-20 and 7-2. The antibodies immunoprecipitate two noncovalently associated glycoprotein chains of Mr 180,000 and Mr 95,000. Under reducing conditions the Mr 180,000 chain is resolved into Mr 150,000 and 32,000 subcomponents. Analysis of N-terminal amino acid sequences indicates homology of the Mr 95,000 chain with the beta3 integrin subunit and homology of the Mr 150,000 chain with the alphaIIb integrin subunit. These antibodies induce catfish thrombocyte aggregation and alteration of cell shape. The data indicate conservation of the megakaryocyte/platelet-restricted CD41/CD61 complex in bony fish.