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Mechanism of Filopodia Formation

Filopodia are thin, actin-rich cellular protrusions that play an important role in many fundamental cellular functions. They vary in their occurrence, length, and positioning in different cell types, suggesting their diverse roles.
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Functional Complementation Analysis (FCA): A Laboratory Exercise Designed and Implemented to Supplement the Teaching of Biochemical Pathways
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Functional characterization of a ficolin-mediated complement pathway in amphioxus.

Huiqing Huang1, Shengfeng Huang, Yingcai Yu

  • 1Department of Biochemistry, College of Life Sciences, State Key Laboratory of Biocontrol, National Engineering Research Center of South China Sea Marine Biotechnology, Sun Yat-sen University, Guangzhou 510275, People's Republic of China.

The Journal of Biological Chemistry
|August 12, 2011
PubMed
Summary

Scientists found a functional ficolin-complement pathway in amphioxus, a primitive chordate. This immune pathway, involving ficolin FCN1 and complement C3, may be a chordate-specific innovation, expanding our understanding of invertebrate immunity.

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Area of Science:

  • Evolutionary immunology
  • Invertebrate biology
  • Complement system research

Background:

  • The ficolin-mediated complement pathway is crucial for vertebrate immunity.
  • Its presence and function in invertebrates, particularly non-chordates, remain largely unknown.
  • Understanding invertebrate immunity provides insights into the evolution of host defense mechanisms.

Purpose of the Study:

  • To investigate the existence and function of a ficolin-complement pathway in the cephalochordate amphioxus.
  • To identify and characterize key ficolin pathway components in amphioxus.
  • To determine if this pathway represents an early evolutionary step in chordates.

Main Methods:

  • Bioinformatic identification of ficolin pathway homologs in amphioxus.
  • Gene expression analysis (RT-qPCR) in response to bacterial infection.
  • Recombinant protein expression and functional assays (hemagglutination, bacterial recognition).
  • Complement C3 activation assays in amphioxus humoral fluid.

Main Results:

  • Identified amphioxus homologs of ficolin (FCN1), serine proteases (MASP1/3), and complement C3.
  • FCN1, MASP1/3, and C3 were highly expressed in mucosal tissues and gonads, upregulated after infection.
  • Recombinant FCN1 acted as a pattern-recognition receptor, binding bacteria.
  • Recombinant MASP1/3 and FCN1 activated amphioxus C3, demonstrating a functional pathway.

Conclusions:

  • Amphioxus possess a functional ficolin-complement pathway, involving FCN1, MASP1/3, and C3.
  • This pathway appears to be a dedicated immune mechanism in amphioxus.
  • The findings suggest the ficolin-complement pathway may be a chordate-specific evolutionary innovation.