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Role of sulfation in the processing of gastric mucins
Y H Liau1, V L Murty, A Slomiany
1Research Center, New Jersey Dental School, University of Medicine and Dentistry of New Jersey, Newark.
Abstract:
The role of sulfation in the processing of mucus glycoprotein in gastric mucosa was investigated. Rat gastric mucosal segments were incubated in MEM at various medium sulfate concentrations in the presence of [35S]Na2SO4, [3H]glucosamine and [3H]proline, with and without chlorate an inhibitor of PAPS formation. The results revealed that the mucin sulfation attained maximum at 300 microM medium sulfate concentration. Introduction of chlorate into the incubation medium, while having no effect on the protein synthesis as evidenced by [3H]proline incorporation, caused at its optimal concentration of 2 mM a 90% decrease in mucin sulfation and a 40% drop in mucin glycosylation. Evaluation of mucin molecular forms distribution indicated the predominance of the high molecular mucin form in the intracellular fraction and the low molecular mucin from in the extracellular fraction. Increase in medium sulfate caused an increase in the high molecular weight mucin form in both fractions, and this effect was inhibited by chlorate. Also, higher medium sulfate concentrations led to a higher degree of sulfation in the high molecular weight mucin form, the effect of which was inhibited by chlorate. The results suggest that the sulfation process is an early event taking place at the stage of mucin subunit assembly and is required for mucin polymer formation. Hence, the disturbances in mucin sulfation process could be detrimental to the maintenance of gastric mucus coat integrity.
Insights
Mucin sulfation is crucial for gastric mucus glycoprotein processing and polymer formation. Impaired sulfation disrupts mucus integrity, potentially harming the gastric mucus coat.
Area of Science:
- Biochemistry
- Cell Biology
- Gastroenterology
Background:
- Gastric mucus glycoproteins (mucin) are vital for protecting the stomach lining.
- The precise role of sulfation in mucin processing remains incompletely understood.
Purpose of the Study:
- To investigate the role of sulfation in gastric mucin processing.
- To determine the impact of sulfate availability on mucin synthesis and assembly.
Main Methods:
- Incubation of rat gastric mucosal segments with radiolabeled precursors ([35S]Na2SO4, [3H]glucosamine, [3H]proline).
- Utilized chlorate, an inhibitor of PAPS formation, to assess sulfation inhibition.
- Analyzed mucin molecular weight distribution and sulfation degree.
Main Results:
- Mucin sulfation peaked at 300 microM medium sulfate.
- Chlorate significantly reduced mucin sulfation (90%) and glycosylation (40%) without affecting protein synthesis.
- Increased medium sulfate promoted high molecular weight mucin forms and enhanced sulfation, effects blocked by chlorate.
Conclusions:
- Sulfation is an early event in mucin subunit assembly, essential for mucin polymer formation.
- Disruptions in mucin sulfation can compromise gastric mucus coat integrity.