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AlphaB-crystallin in the rat lens is phosphorylated at an early post-natal age
1Department of Biochemistry, Institute for Developmental Research, Aichi Human Service Center, Kasugai, Japan. itohide@inst-hsc.pref.aichi.jp
Insights
Phosphorylation of alphaB-crystallin in rat lenses increases after birth, with Ser-45 being preferentially phosphorylated. This is driven by the developmental activation of p44/42 MAP kinase.
Area of Science:
- Ophthalmology
- Developmental Biology
- Molecular Biology
Background:
- AlphaB-crystallin is a small heat shock protein crucial for lens transparency.
- Its phosphorylation state can change during development and in response to stress.
- Understanding these changes is important for lens health.
Purpose of the Study:
- To investigate the developmental changes in alphaB-crystallin phosphorylation in rat lenses.
- To identify specific phosphorylation sites and their developmental regulation.
- To explore the role of MAP kinase in this process.
Main Methods:
- Isoelectric focusing gel electrophoresis and SDS-PAGE were used to separate protein forms.
- Western blot analysis with specific antibodies identified phosphorylated serine residues (Ser-19, Ser-45, Ser-59).
- Levels of active p44/42 MAP kinase were also assessed.
Main Results:
- Phosphorylated alphaB-crystallin was low at birth, increasing by 3 weeks and plateauing at 8 weeks.
- Phosphorylation at Ser-45 was the predominant modification observed.
- Active p44/42 MAP kinase levels increased developmentally, correlating with Ser-45 phosphorylation.
Conclusions:
- AlphaB-crystallin phosphorylation increases significantly during postnatal lens development in rats.
- The developmental increase in Ser-45 phosphorylation is mediated by the activation of p44/42 MAP kinase.
- These findings highlight a specific molecular mechanism regulating alphaB-crystallin during lens maturation.
Abstract:
We determined the developmental changes in the phosphorylation state of alphaB-crystallin in lenses from rats at various post-natal ages by isoelectric focusing gel electrophoresis or sodium dodecyl sulfate-polyacrylamide gel electrophoresis and a subsequent Western blot analysis of extracts of lenses using antibodies that recognized the carboxy-terminal sequence or each of the three phosphorylated serine residues (Ser-19, Ser-45 and Ser-59) in alphaB-crystallin. Phosphorylated forms of alphaB-crystallin were barely detected at birth but they became detectable at 3 weeks of age and reached plateau levels at 8 weeks of age. The phosphorylation of alphaB-crystallin at Ser-45 was observed preferentially. The active form of p44/42 MAP kinase, which is responsible for the phosphorylation of Ser-45 in alphaB-crystallin, also increased in a development-dependent manner. Thus we found that the developmental increase of the phosphorylation at Ser-45 of alphaB-crystallin in the rat lens was due to the developmental activation of p44/42 MAP kinase.