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The myelin-associated glycoprotein is phosphorylated in the peripheral nervous system
H C Agrawal1, A B Noronha, D Agrawal
1Department of Pediatrics, Washington University School of Medicine, St. Louis, MO.
Abstract:
Phosphorylation of the myelin-associated glycoprotein (MAG) in the peripheral nervous system is demonstrated by immunoprecipitation from myelin proteins radiolabeled in vivo, in nerve slices and in a cell-free system. Phosphoamino acid analysis of immunoprecipitated MAG revealed the presence of radioactivity in phosphoserine, but not in phosphothreonine or phosphotyrosine. Only the shorter isoform of MAG (S-MAG) was detected by immunostaining of nitrocellulose sheets with anti-MAG anti-serum after enzymatic deglycosylation of immunoprecipitated MAG labeled in nerve slices. Autoradiography of the same Western blots revealed that most of the radioactive phosphate was in S-MAG, demonstrating that the polypeptide backbone of S-MAG is phosphorylated in the PNS.
Insights
Phosphorylation of myelin-associated glycoprotein (MAG) occurs in the peripheral nervous system, specifically on phosphoserine residues of the shorter MAG isoform (S-MAG). This indicates S-MAG
Area of Science:
- Neuroscience
- Cell Biology
- Biochemistry
Background:
- Myelin-associated glycoprotein (MAG) plays a crucial role in the peripheral nervous system (PNS).
- Post-translational modifications like phosphorylation can regulate protein function.
Purpose of the Study:
- To investigate the phosphorylation status of MAG in the PNS.
- To identify the specific sites and isoforms of MAG that undergo phosphorylation.
Main Methods:
- In vivo and in vitro radiolabeling of myelin proteins.
- Immunoprecipitation of MAG.
- Phosphoamino acid analysis.
- Enzymatic deglycosylation and Western blotting with anti-MAG antibodies.
Main Results:
- Phosphorylation of MAG was detected in the PNS using various experimental systems.
- Phosphoamino acid analysis confirmed phosphorylation occurs on serine residues.
- The shorter MAG isoform (S-MAG) was identified as the primary site of phosphorylation.
- Radioactive phosphate was predominantly localized to the S-MAG polypeptide backbone.
Conclusions:
- The polypeptide backbone of S-MAG is phosphorylated in the PNS.
- Phosphorylation of S-MAG on serine residues may be important for its function in the peripheral nervous system.