Ligand-binding activity and expression profile of annexins in Caenorhabditis elegans
Sara Nishioka1, Jun-ichi Aikawa, Michiru Ida
1Graduate School of Humanities and Sciences, Ochanomizu University, 2-1-1 Otsuka, Bunkyo-ku, Tokyo 112-8610, Japan.
Abstract:
Mammalian annexins are implicated in several physiological mechanisms based on their calcium-dependent phospholipid/membrane binding and carbohydrate-binding activities. In this study, we investigated gene expression profiles of all four Caenorhabditis elegans annexins, nex-1, -2, -3 and -4, throughout the development, and compared phospholipid- and carbohydrate-binding properties of their protein products, NEX-1, -2, -3 and -4. We found that nex-1 and -3 are transcribed continuously during the developmental stages, while expression of nex-2 and -4 appeared to be temporal, peaking at the L1 stage followed by a gradual decrease toward the adult stage. NEX-1 and -3 were detected as single protein band in total worm extracts by immunoblotting, but NEX-2 was heterogenic in size. NEX-1, -2, and -3 showed the binding activities to phosphatidylserine, phosphatidylinositol and phosphatidylethanolamine, but not to phosphatidylcholine. In contrast to their uniform phospholipids-binding properties, their glycosaminoglycan-binding activities were distinctive. NEX-2 bound to heparan sulfate and chondroitin, NEX-3 bound only to heparan sulfate, and NEX-1 showed no lectin activities under tested conditions. NEX-4 had neither phospholipids- nor carbohydrate-binding properties. Differentiated expression profiles and ligand-binding properties of NEX-1, -2, -3 and -4, shown in our study, may represent distinctive roles for each C. elegans annexins.
Insights
This study reveals distinct developmental expression and ligand-binding properties for Caenorhabditis elegans annexins (NEX-1, -2, -3, -4). These differences suggest unique physiological roles for each annexin in the nematode.
Area of Science:
- Molecular Biology
- Developmental Biology
- Biochemistry
Background:
- Mammalian annexins are crucial for physiological processes via calcium-dependent membrane binding.
- Understanding annexin function in model organisms like C. elegans provides insights into conserved biological mechanisms.
Purpose of the Study:
- To investigate the gene expression profiles of all four Caenorhabditis elegans annexins (nex-1, -2, -3, -4) during development.
- To compare the phospholipid- and carbohydrate-binding properties of the NEX-1, -2, -3, and -4 proteins.
Main Methods:
- Analysis of gene expression patterns throughout C. elegans development.
- Immunoblotting to detect protein expression and size heterogeneity.
- In vitro assays to assess binding affinities to various phospholipids and glycosaminoglycans.
Main Results:
- nex-1 and nex-3 exhibited continuous transcription, while nex-2 and nex-4 showed temporal expression peaking at the L1 larval stage.
- NEX-1, NEX-2, and NEX-3 bound to specific phospholipids (phosphatidylserine, phosphatidylinositol, phosphatidylethanolamine), but not phosphatidylcholine.
- Distinct glycosaminoglycan-binding activities were observed: NEX-2 bound heparan sulfate and chondroitin, NEX-3 bound only to heparan sulfate, and NEX-1 showed no lectin activity. NEX-4 lacked both phospholipid and carbohydrate binding.
Conclusions:
- The differentiated expression profiles and specific ligand-binding capabilities of C. elegans annexins (NEX-1, -2, -3, -4) indicate specialized functions for each protein.
- These findings contribute to understanding the diverse roles of annexins in nematode physiology and development.
