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Site-specific cleavage of basement membrane collagen IV during Drosophila metamorphosis
L I Fessler1, M L Condic, R E Nelson
1Molecular Biology Institute, University of California, Los Angeles 90024-1570.
Abstract:
Breakdown of basement membranes is an important step in the controlled rearrangement of cells during metamorphosis, cell migration, and metastatic spread of tumor cells. One of our two laboratories found a unique collagenous peptide that only appears during metamorphosis of Drosophila melanogaster. The other laboratory previously reported that during 20-hydroxyecdysone-induced eversion of Drosophila imaginal discs a glycoprotein named gp125 arises (Birr et al., 1990). We show that these two peptides are identical and that they are formed from basement membrane collagen IV. Cleavage occurs at an imperfection of this homotrimeric collagen helix between residues 755/756 in the sequence CALDE/IKMPAK. The peptide is the carboxyl fragment, 100,647 M(r), as derived from the amino acid sequence of the collagen alpha 1(IV) chain. The corresponding amino fragment was also recovered from a disulfide-linked aggregate. This specific cleavage supports the concept of highly targeted, controlled breakdown of basement membranes during metamorphosis. Furthermore, these cuts occur at strategic sites of the predicted supramolecular network of collagen IV molecules of Drosophila basement membranes.
Insights
Researchers identified a specific collagen peptide during Drosophila metamorphosis, originating from basement membrane collagen IV. This finding reveals targeted basement membrane breakdown during development.
Area of Science:
- Developmental Biology
- Cell Biology
- Biochemistry
Background:
- Basement membrane breakdown is crucial for cell rearrangement during metamorphosis, cell migration, and tumor metastasis.
- A unique collagenous peptide appears during Drosophila melanogaster metamorphosis.
- A glycoprotein, gp125, arises during 20-hydroxyecdysone-induced eversion of Drosophila imaginal discs.
Purpose of the Study:
- To identify the unique collagenous peptide found during Drosophila metamorphosis.
- To determine the origin and function of gp125.
- To elucidate the precise mechanism of basement membrane collagen IV cleavage during metamorphosis.
Main Methods:
- Biochemical analysis of peptides isolated during Drosophila metamorphosis.
- Comparison of the unique collagenous peptide with gp125.
- Amino acid sequencing to identify cleavage sites in collagen IV.
Main Results:
- The unique collagenous peptide and gp125 are identical.
- This peptide is derived from basement membrane collagen IV.
- Cleavage occurs at a specific imperfection in the collagen IV helix, yielding a carboxyl fragment (100,647 M(r)) and an amino fragment.
Conclusions:
- The identified cleavage event is highly specific and targeted.
- This process supports controlled basement membrane breakdown during metamorphosis.
- The cleavage sites are strategically located within the predicted collagen IV network in Drosophila basement membranes.