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Glycoprotein mannosylation in rat liver nuclei
Y Fayet1, S Galland, A Degiuli
1Laboratoire de Biochimie des Membranes LBTM--CNRS, Villeurbane--France.
Biochemistry International
|March 1, 1988
Summary
Retinyl phosphate facilitates mannose transfer to glycoproteins in non-nuclear membranes, but not in nuclei. This suggests distinct mannosylation pathways in different cellular compartments.
Area of Science:
- Cell Biology
- Biochemistry
- Membrane Biology
Background:
- Glycoprotein synthesis involves the transfer of mannose residues.
- Retinyl phosphate is a potential mannose donor in cellular processes.
- Differential functions of nuclear and non-nuclear membranes are crucial for cell biology.
Purpose of the Study:
- To investigate the role of retinyl phosphate in mannosylation reactions within cellular membranes.
- To compare the mannosylation capabilities of nuclei and non-nuclear membranes.
- To identify the dependence of mannose transfer on retinyl phosphate in different membrane fractions.
Main Methods:
- In vitro transfer of (14C)mannose from GDP-(14C)mannose to endogenous acceptors.
- Incubation of nuclei and non-nuclear membranes with and without exogenous retinyl phosphate.
- Electrophoretic analysis of labeled glycoprotein acceptors.
Main Results:
- Retinyl phosphate mediated the labeling of specific endogenous acceptors exclusively in non-nuclear membranes.
- Mannosylation in nuclei was independent of exogenous retinyl phosphate.
- Electrophoretic profiles of labeled acceptors differed significantly between nuclear and non-nuclear membranes, indicating distinct protein targets.
Conclusions:
- Non-nuclear membranes utilize a retinyl phosphate-dependent pathway for mannosylation.
- Nuclear mannosylation pathways are distinct and do not rely on retinyl phosphate.
- These findings highlight compartment-specific mechanisms in glycoprotein modification.