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R15 alpha 1 and R 15 alpha 2 peptides from Aplysia: comparison of bioactivity, distribution, and function of two
A Alevizos1, D Karagogeos, K R Weiss
1Department of Physiology and Cellular Biophysics, Columbia University, New York, New York 10032.
Abstract:
The mRNA precursor encoded by the R15 gene is alternatively spliced in different neurons to form two related variants, R15-1 and R15-2 mRNA. One of the peptides encoded by the R15-2 mRNA, the R15 alpha 1 peptide, is expressed in the endogenously bursting neuron R15 and mediates some of its central and peripheral synaptic actions. In this study we found that the R15 alpha 2 peptide, which is encoded by the R15-1 mRNA, is synthesized in other neurons in the abdominal ganglion and is also bioactive. The R15 alpha 1 and R15 alpha 2 peptides were found to exert many similar actions on the cardiovascular, digestive, respiratory, and reproductive systems. However, the differences between many of the pharmacological effects of the R15 alpha 1 and R15 alpha 2 peptides indicate that alternative splicing in this system results in two functionally different peptides. Widespread immunoreactivity was found for an antibody directed against the R15 alpha 2 peptide, both in the central nervous system and the periphery. But because of the shared sequence with the R15 alpha 1 peptide, the antibody cross-reacts with the R15 alpha 1 peptide. To distinguish immunocytochemically between the two peptides, we also raised a second antibody that recognizes only the R15 alpha 1 peptide. This antibody labeled the cell body of only one neuron in the central nervous system, R15, although widespread immunoreactivity was found in axons and varicosities in the periphery.
Insights
Alternative splicing of R15 gene mRNA creates two distinct peptides, R15 alpha 1 and R15 alpha 2. These peptides, while similar, exhibit unique pharmacological effects, highlighting functional divergence from alternative splicing.
Area of Science:
- Neuroscience
- Molecular Biology
- Genetics
Background:
- The R15 gene produces mRNA precursors that undergo alternative splicing.
- This splicing generates two mRNA variants, R15-1 and R15-2.
- R15-2 mRNA encodes the R15 alpha 1 peptide, active in specific neurons.
Purpose of the Study:
- To investigate the bioactivity and distribution of the R15 alpha 2 peptide.
- To compare the functional effects of R15 alpha 1 and R15 alpha 2 peptides.
- To develop methods for distinguishing between the two peptides in neural tissues.
Main Methods:
- Peptide synthesis and characterization.
- Pharmacological assays on various physiological systems.
- Immunocytochemistry using specific antibodies.
Main Results:
- R15 alpha 2 peptide, encoded by R15-1 mRNA, is bioactive and found in other neurons.
- Both peptides affect cardiovascular, digestive, respiratory, and reproductive systems.
- Distinct pharmacological profiles suggest functional differences arising from alternative splicing.
- Antibody cross-reactivity complicated initial immunocytochemical analysis.
Conclusions:
- Alternative splicing of R15 mRNA yields functionally distinct peptides (R15 alpha 1 and R15 alpha 2).
- These peptides mediate diverse physiological actions.
- Specific antibodies are crucial for differentiating peptide localization and function.