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Identification of GTP-binding proteins in myelin and oligodendrocyte membranes
P E Braun1, E Horvath, V W Yong
1Department of Biochemistry, McGill University, Montreal, Quebec, Canada.
Abstract:
Myelin membranes purified from mouse and rat brain are associated with alpha subunits of four signal transducing guanosine triphosphate (GTP)-binding proteins: Go, Gi, Gs, and ras. Four low-molecular-weight (Mr) GTP-binding proteins are also present, as demonstrated by the binding of GTP to proteins immobilized in nitrocellulose. This latter group is more prominent at early stages of myelination and remains associated with isolated myelin membranes despite repetitive cycles of purification. At least one nonmyelin subcellular membrane fraction possesses the same proteins. The total membrane fraction of cultured oligodendrocytes is associated with both groups of GTP-binding proteins. None of the well-known myelin proteins bound GTP by the procedure described.
Insights
Myelin membranes contain signal-transducing guanosine triphosphate (GTP)-binding proteins, including ras. These GTP-binding proteins are prominent during early myelination and found in cultured oligodendrocytes.
Area of Science:
- Neuroscience
- Cell Biology
- Biochemistry
Background:
- Myelin, the insulating sheath around nerve fibers, is crucial for efficient neural signal transmission.
- Signal transduction pathways involving guanosine triphosphate (GTP)-binding proteins (G proteins) play vital roles in cellular processes.
- The specific molecular composition and function of proteins associated with myelin membranes, particularly during development, are areas of ongoing research.
Purpose of the Study:
- To identify and characterize GTP-binding proteins associated with purified myelin membranes from rodent brains.
- To investigate the presence and developmental relevance of these GTP-binding proteins in myelin.
- To examine the association of GTP-binding proteins with oligodendrocytes, the myelin-producing cells.
Main Methods:
- Purification of myelin membranes from mouse and rat brain tissue.
- GTP-binding assays using immobilized proteins on nitrocellulose to detect GTP-binding proteins.
- Analysis of protein fractions from myelin, non-myelin membranes, and cultured oligodendrocytes.
Main Results:
- Purified myelin membranes are associated with alpha subunits of four signal-transducing GTP-binding proteins: Go, Gi, Gs, and ras.
- Four low-molecular-weight GTP-binding proteins were identified and remained associated with myelin membranes through multiple purification steps.
- These low-molecular-weight GTP-binding proteins were more abundant during early myelination stages and were also found in non-myelin fractions and cultured oligodendrocytes.
Conclusions:
- Myelin membranes are associated with both signal-transducing and low-molecular-weight GTP-binding proteins.
- The presence of these proteins, particularly during early myelination, suggests a potential role in myelin development or function.
- The association of these GTP-binding proteins with oligodendrocytes further supports their involvement in myelin-related processes.