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Effect of propionic and methylmalonic acids on the in vitro phosphorylation of intermediate filaments from cerebral
Lúcia Maria Vieira de Almeida1, Cláudia Funchal, Priscila de Lima Pelaez
1Universidade Federal do Rio Grande do Sul, Instituto de Ciências Básicas da Saude, Departamento de Bioquímica, Rua Ramiro Barcelos 2600 anexo, 90035-003 Porto Alegre, RS, Brazil.
Abstract:
In this study we investigated the in vivo and in vitro effects of methylmalonic (MMA) and propionic acids (PA), at concentrations usually found in methylmalonic acidemia and propionic acidemia respectively, on the phosphorylation of intermediate filament proteins in cerebral cortex of rats during development. Rats of 9, 12, and 17 days were acutely injected with the acids and sacrificed 90 min after injection. The cerebral cortex was dissected, and slices were incubated with 32P-orthophosphate. The cytoskeletal fraction was extracted and the radioactivity incorporated into intermediate filament subunits was measured. In addition, cortical slices from nontreated rats of 9, 12, 15, 17, 21, and 60 days of life were incubated with the acids in the presence of 32P-orthophosphate, the cytoskeletal fraction was extracted and the radioactivity was measured. Results demonstrated that MMA and PA significantly decreased the radioactivity incorporated into intermediate filament proteins at day 12, both in vivo and in tissue slices. In contrast, PA increased the in vitro phosphorylation of the cytoskeletal proteins in slices of 21-day-old animals. It acts through PP2A and PP2B in 12-day-old rats and through PKA and PKCaMII in 21-day-old animals. We propose that alteration of cytoskeletal protein phosphorylation caused by methylmalonic and propionic acids may be related to the neurological dysfunction characteristic of propionic and methylmalonic acidemia.
Insights
Methylmalonic acid (MMA) and propionic acid (PA) disrupt intermediate filament protein phosphorylation in developing rat brains. These changes may explain neurological issues seen in methylmalonic acidemia and propionic acidemia.
Area of Science:
- Biochemistry
- Neuroscience
- Developmental Biology
Background:
- Methylmalonic acidemia and propionic acidemia are inherited metabolic disorders.
- Neurological dysfunction is a common symptom in these conditions.
- The underlying molecular mechanisms, particularly concerning the brain's developing cytoskeleton, remain unclear.
Purpose of the Study:
- To investigate the effects of methylmalonic acid (MMA) and propionic acid (PA) on protein phosphorylation in the developing rat brain.
- To determine if these effects are linked to neurological symptoms in acidemia patients.
Main Methods:
- In vivo and in vitro studies using rat cerebral cortex slices from different developmental stages (9-60 days).
- Rats were injected with MMA or PA, or brain slices were incubated with these acids.
- Phosphorylation levels of intermediate filament proteins were measured using 32P-orthophosphate incorporation.
Main Results:
- MMA and PA significantly reduced intermediate filament protein phosphorylation in 12-day-old rats (both in vivo and in vitro).
- PA increased cytoskeletal protein phosphorylation in 21-day-old rat brain slices.
- Specific protein phosphatases (PP2A, PP2B) and kinases (PKA, PKCaMII) were implicated depending on age.
Conclusions:
- Alterations in cytoskeletal protein phosphorylation by MMA and PA may contribute to the neurological dysfunction observed in methylmalonic acidemia and propionic acidemia.
- These findings highlight a potential molecular pathway linking metabolic disturbances to neurodevelopmental deficits.
