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Updated: Sep 3, 2025
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Purification of the Membrane Compartment for Endoplasmic Reticulum-associated Degradation of Exogenous Antigens in Cross-presentation
Published on: August 21, 2017
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Regulated processing and secretion of a peptide precursor in cilia
Raj Luxmi1, Richard E Mains2, Betty A Eipper1,2
1Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT 06030-3305.
Summary
Green algae use ciliary ectosomes for peptide secretion, a process distinct from animal cells. This study reveals how propeptide processing and amidated peptide formation occur on these specialized vesicles.
Area of Science:
- Cell Biology
- Molecular Biology
- Evolutionary Biology
Background:
- Cilia function as sensory and secretory organelles, releasing bioactive products via ectosomes.
- Peptidergic intercellular communication is ancient and widespread across eukaryotes.
- Chlamydomonas reinhardtii possesses genes for peptide processing but lacks typical animal dense-core vesicles.
Purpose of the Study:
- To investigate the hypothesis that Chlamydomonas reinhardtii uses ciliary ectosomes for propeptide processing and secretion.
- To dissect the pathway for forming an amidated peptidergic sexual signal on ciliary ectosomes.
- To gain insights into the evolution of peptidergic signaling.
Main Methods:
- Bioinformatic analysis of peptide precursors and processing enzymes.
- Mass spectrometry to identify processed peptides and enzymes in cilia and ectosomes.
- Biochemical analysis of posttranslational modifications.
Main Results:
- Identified stable domains in the proGATI precursor, unlike metazoan propeptides.
- Linked endoproteolytic cleavage to ectosome entry via mass spectrometry of convertases and amidated products.
- Demonstrated extensive posttranslational modification of proGATI, conferring stability to the amidated product.
Conclusions:
- Chlamydomonas reinhardtii utilizes ciliary ectosomes for regulated secretion of amidated peptides.
- This pathway provides an alternative to dense-core vesicles for peptide processing and release.
- The findings illuminate the evolution of peptidergic signaling and metazoan ciliary secretion.
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