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Acylation of myelin Po protein is required for adhesion
Y Gao1, W Li, M T Filbin
1Biology Department, Hunter College, The City University of New York, New York 10021, USA.
Abstract:
The extracellular domains of myelin Po protein interact homophilically and hence hold myelin compact at the intraperiod line. The cytoplasmic domain of Po, however, can also affect the interactions of its extracellular sequences. Po is acylated, mostly with palmitic acid, at Cys 153, just at the transmembrane:cytoplasmic domain interface. Here we show that Po mutated at Cys 153 to alanine (C153A), is not acylated and is not adhesive. Like wild-type Po, C153A Po clusters within the membrane and seems to interact with the cytoskeleton. On the other hand, the rate of turnover of C153A Po in transfected Chinese hamster ovary cells is almost 4 times faster than wild-type Po. The increased instability of C153A Po compared to wild-type Po may account for its loss of adhesion.
Insights
Myelin Po protein acylation at Cys 153 is crucial for its adhesion. Mutating this site (C153A) prevents acylation and causes instability, leading to loss of myelin adhesion.
Area of Science:
- Neuroscience
- Molecular Biology
- Biochemistry
Background:
- Myelin Po protein is essential for compacting myelin sheaths in the nervous system.
- The extracellular domains of Po mediate homophilic interactions, maintaining myelin structure.
- The cytoplasmic domain and post-translational modifications, like acylation, can influence Po protein function.
Purpose of the Study:
- To investigate the role of Cys 153 acylation in the adhesive properties and stability of myelin Po protein.
- To determine if mutations at Cys 153 affect Po protein's interaction with the cytoskeleton or its membrane clustering.
Main Methods:
- Site-directed mutagenesis was used to create a Cys 153 to alanine (C153A) mutant of the Po protein.
- Acylation status, adhesion, membrane clustering, and cellular turnover rates of wild-type and C153A Po were analyzed in transfected Chinese hamster ovary cells.
Main Results:
- The C153A Po mutant was not acylated and exhibited a significant loss of adhesive properties.
- C153A Po, similar to wild-type Po, showed membrane clustering and interaction with the cytoskeleton.
- The cellular turnover rate of C153A Po was approximately four times faster than that of wild-type Po, indicating increased instability.
Conclusions:
- Acylation of myelin Po protein at Cys 153 is critical for its adhesive function.
- The increased instability and rapid turnover of the non-acylated C153A Po mutant likely contribute to its inability to maintain myelin adhesion.