Related Experiment Video

Updated: Jul 3, 2026

Stimulation of Stem Cell Niches and Tissue Regeneration in Mouse Skin by Switchable Protoporphyrin IX-Dependent Photogeneration of Reactive Oxygen Species In Situ
10:05

Stimulation of Stem Cell Niches and Tissue Regeneration in Mouse Skin by Switchable Protoporphyrin IX-Dependent Photogeneration of Reactive Oxygen Species In Situ

Published on: May 8, 2020

A positive feedback mechanism in the Manduca sexta prophenoloxidase activation system

Yang Wang1, Haobo Jiang

  • 1Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078, USA.

Insect Biochemistry and Molecular Biology
|July 16, 2008
PubMed

Insights

A minute amount of PAP1 significantly boosted phenoloxidase (PO) activity in Manduca sexta plasma, revealing a self-reinforcing immune defense mechanism. This suggests other plasma proteins are crucial for optimal proPO activation and pathogen defense.

Area of Science:

  • * Insect immunity
  • * Biochemistry
  • * Serine proteinase cascades

Background:

  • * Pathogen recognition in Manduca sexta initiates a serine proteinase cascade.
  • * This cascade generates active phenoloxidase (PO) via proPO-activating proteinase (PAP) and serine proteinase homologs (SPHs).
  • * Active PO is vital for antimicrobial defense, wound healing, and melanin synthesis.

Purpose of the Study:

  • * To investigate the effect of PAP1 on proPO activation in naive Manduca sexta plasma.
  • * To elucidate the proteolytic events involved in enhanced proPO activation.
  • * To identify potential self-reinforcing mechanisms within the proPO activation system.

Main Methods:

  • * Incubation of PAP1 with plasma from naive Manduca sexta larvae.
  • * In vitro incubation of PAP1, proPO, and SPHs.
  • * Analysis of proteolytic activation of various protein precursors (HP6, HP8, PAP1, SPH1, SPH2, PO).
  • * Comparison of protein cleavage patterns in plasma versus in vitro conditions.

Main Results:

  • * A small amount of PAP1 dramatically increased PO activity in naive plasma, exceeding in vitro reactions.
  • * Enhanced proPO activation was associated with proteolytic activation of HP6, HP8, PAP1, SPH1, SPH2, and PO precursors.
  • * PAP1 specifically cleaved proSPH2 and partially hydrolyzed proHP6 and proHP8 at unique sites compared to plasma activation.
  • * PAP1 did not directly activate proPAP1.

Conclusions:

  • * A self-reinforcing mechanism exists within the Manduca sexta proPO activation system.
  • * Plasma proteins, beyond PAP1, are necessary for efficient cleavage of proHP6 and proHP8.
  • * These findings suggest a complex regulatory network for strengthening immune responses during early pathogen encounters.

More Related Videos

Light-mediated Reversible Modulation of the Mitogen-activated Protein Kinase Pathway during Cell Differentiation and Xenopus Embryonic Development09:32

Light-mediated Reversible Modulation of the Mitogen-activated Protein Kinase Pathway during Cell Differentiation and Xenopus Embryonic Development

Published on: June 15, 2017

Pattern-Triggered Oxidative Burst and Seedling Growth Inhibition Assays in Arabidopsis thaliana04:11

Pattern-Triggered Oxidative Burst and Seedling Growth Inhibition Assays in Arabidopsis thaliana

Published on: May 21, 2019

Related Concept Videos

Cell Signaling Feedback Loops01:07

Cell Signaling Feedback Loops

Positive and negative feedback loops are crucial for regulating biological signaling systems. These feedback loops are processes that connect output signals to their inputs.
Negative feedback loops
Most signaling systems have negative feedback loops that can perform different functions such as output limiter, and adaptation.
Output limiter
Upon receiving an input signal, the cellular response rapidly increases until a threshold is reached. Beyond this threshold, a negative feedback loop...
Positive and Negative Feedback Loops01:18

Positive and Negative Feedback Loops

Animal organs and organ systems constantly adjust to internal and external changes through a process called homeostasis ("steady state"). Examples of these changes include regulation of the level of glucose or calcium in the blood or internal responses to external temperatures. Homeostasis requires  maintaining an internal dynamic equilibrium:
Amplifying Signals via Enzymatic Cascade01:22

Amplifying Signals via Enzymatic Cascade

When a ligand binds to a cell-surface receptor, the receptor's intracellular domain changes shape, which may either activate its enzyme function or allow its binding to other molecules. The initial signal is amplified by most signal transduction pathways. This means that a single ligand molecule can activate multiple molecules of a downstream target. Proteins that relay a signal are most commonly phosphorylated at one or more sites, activating or inactivating the protein. Kinases catalyze the...
Feedback Loops01:01

Feedback Loops

In most cases, excessive hormone production is prevented by negative feedback—a loop that starts with a stimulus inducing the release of a particular substance, like a hormone, to maintain a certain level before triggering a signal that results in a decrease in further release of the hormone.
The Antenna Complex01:15

The Antenna Complex

Plants and other photosynthetic organisms comprise pigments capable of absorption of direct sunlight. These pigments are present in the reaction center - the main site of photochemical reactions as well as in the antenna complex. Under average light conditions, the rate at which reaction center pigments absorb light is far below the electron transport chain's capacity. As a result, the reaction center alone cannot provide enough energy to drive photosynthesis. The photosynthetic efficiency can...
The Photochemical Reaction Center01:29

The Photochemical Reaction Center

Reaction centers are pigment-protein complexes that initiate energy conversion from photons to chemical entities. Therefore, photochemical reaction center is a more appropriate term that describes these complexes. The Nobel laureates Robert Emerson and William Arnold provided the first experimental evidence of photochemical reaction centers by demonstrating the participation of nearly 2,500 chlorophyll molecules for the release of just one molecule of oxygen. Despite thousands of photosynthetic...