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Immune properties of invertebrate phenoloxidases

Lage Cerenius1, Kenneth Söderhäll1

  • 1Department of Organismal Biology,Uppsala University, Norbyvägen 18A, 752 36 Uppsala, Sweden.

Developmental and Comparative Immunology
|April 15, 2021
PubMed

Insights

Phenoloxidases (POs) are crucial for invertebrate immunity, offering protection against pathogens through melanin production. Arthropod proPO also provides non-melanic immune functions, highlighting its diverse role in host defense.

Area of Science:

  • Invertebrate immunology
  • Biochemistry
  • Molecular biology

Background:

  • Phenoloxidases (POs) are key enzymes in invertebrate immunity, primarily known for melanin production that defends against pathogens.
  • Arthropod prophenoloxidase (proPO) exhibits diverse immune activities beyond melanization, including cytokine, opsonin, and microbiocidal functions.
  • The activation of proPO and its processing into peptide fragments parallels aspects of the vertebrate complement system, despite lacking sequence homology.

Purpose of the Study:

  • To explore the multifaceted roles of phenoloxidases (POs) in invertebrate immunity.
  • To investigate the non-melanic immune functions of arthropod prophenoloxidase (proPO).
  • To understand how pathogens interact with and manipulate the proPO system.

Main Methods:

  • Analysis of phenoloxidase (PO) and prophenoloxidase (proPO) activities in various invertebrate species.
  • Investigating the proteolytic processing of proPO and its activating enzymes.
  • Examining pathogen-derived compounds that target the proPO system.

Main Results:

  • Melanin production by POs provides broad-spectrum immunity against viruses, microorganisms, and parasites.
  • Arthropod proPO possesses intrinsic cytokine, opsonin, and microbiocidal activities, independent of melanin synthesis.
  • Pathogens can modulate proPO activation, influencing the type of immune response generated.
  • Specialized pathogens produce compounds that specifically target and interfere with the proPO system.
  • Phylogenetically distinct POs in non-arthropod invertebrates are involved in melanization against intruders.

Conclusions:

  • Phenoloxidases (POs) are versatile immune effectors in invertebrates, with arthropod proPO playing a central role beyond melanization.
  • The proPO system's activation and function are dynamically regulated by pathogen interactions, representing a sophisticated defense mechanism.
  • Understanding the proPO system offers insights into invertebrate immune strategies and potential therapeutic targets against pathogens.
Keywords:
Complement systemInnate immunityMelaninizationPattern recognitionPhenoloxidaseTyrosinase

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