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Developmental regulation and effect of early undernutrition on phosphorylation of rat cortical synaptic membrane
1Department of Biochemistry, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India. tryambak@bcs.rochester.edu
Insights
Early life undernutrition in rats significantly impacts synaptic protein phosphorylation, particularly tyrosine residues. Nutritional recovery largely reverses these effects, suggesting a link to lipid biosynthesis and membrane fluidity.
Area of Science:
- Neuroscience
- Biochemistry
- Developmental Biology
Background:
- Early postnatal undernutrition is a critical factor influencing brain development.
- Synaptic membrane protein phosphorylation plays a vital role in neuronal function.
- The impact of early nutritional deficits on synaptic protein phosphorylation remains incompletely understood.
Purpose of the Study:
- To investigate the effects of early undernutrition on endogenous protein phosphorylation in rat cerebral cortex synaptic membranes.
- To identify specific proteins and phosphorylation sites affected by early nutritional deficits.
- To explore the relationship between undernutrition, synaptic membrane lipid composition, and protein phosphorylation.
Main Methods:
- Rats were subjected to dietary restriction during early postnatal life to induce undernutrition.
- Synaptic membrane fractions were isolated from the cerebral cortex of normal and undernourished rats.
- Endogenous protein phosphorylation levels were analyzed, focusing on age-dependent changes and specific protein targets (48-, 52-, 61-, 74-kDa proteins) and tyrosine residues.
- Lipid content, including cholesterol-phospholipid ratio, and membrane fluidity were assessed.
Main Results:
- Early undernutrition altered synaptic membrane protein phosphorylation in an age-dependent manner, with significant effects on 48-, 52-, 61-, and 74-kDa proteins, primarily at tyrosine residues.
- Nutritional rehabilitation following early undernutrition largely restored normal synaptic protein phosphorylation patterns.
- Undernutrition induced changes in the cholesterol-phospholipid ratio and fluidity of synaptic membranes, mirroring alterations in protein phosphorylation.
Conclusions:
- Early life undernutrition profoundly affects synaptic protein phosphorylation, with tyrosine phosphorylations being particularly vulnerable.
- The observed changes in protein phosphorylation are closely linked to alterations in synaptic membrane lipid composition and fluidity.
- Lipid biosynthesis pathways are implicated as a mechanism through which early undernutrition impacts synaptic membrane protein phosphorylation and neuronal function.
Abstract:
Undernutrition during early postnatal life was employed in rats by restricting the feeding time. The synaptic membrane fraction from cerebral cortex of normal and undernourished rats of various ages was prepared and endogenous protein phosphorylation studied. Many of the synaptic membrane proteins were found to be phosphorylated in an age-dependent manner. Early undernutrition affects the phosphorylation of various proteins in a complex way; most affected were 48-, 52-, 61- and 74-kDa proteins. These proteins were found to have phosphorylations mainly at tyrosine residues. This finding indicates that tyrosine phosphorylations may be affected most by early undernutrition. Adequate nutrition after early undernutrition removes most of the effects of undernutrition on synaptic protein phosphorylation. To address the question of how undernutrition may affect protein phosphorylation, we studied the lipid content of synaptic membrane fraction as it can affect membrane properties, including the fluidity. We found that undernutrition affects phosphorylation of most of the synaptic membrane proteins in the same manner in which it affects the cholesterol-phospholipid ratio of synaptic membrane and, hence, the fluidity of the membrane. This indicates that lipid biosynthesis is one of the ways by which undernutrition can affect synaptic membrane protein phosphorylation.