Microtubule-associated protein tau is phosphorylated by protein kinase C on its tubulin binding domain

Area of Science:

• Neuroscience
• Biochemistry
• Molecular Biology

Background:

• Tau protein is crucial for microtubule stability.
• Aberrant tau phosphorylation is implicated in neurodegenerative diseases like Alzheimer's.
• Understanding tau phosphorylation sites and their functional consequences is vital.

Purpose of the Study:

• To investigate the in vitro phosphorylation of tau protein by various kinases.
• To identify specific phosphorylation sites and their functional impact on tau-tubulin binding.

Main Methods:

• In vitro kinase assays using purified tau protein.
• Peptide mapping and limited proteolysis to identify phosphorylation sites.
• Analysis of synthetic tau peptides using protein kinase C.
• Assessment of tau-peptide binding to tubulin.

Main Results:

• Multiple kinases, including protein kinase C (PKC), phosphorylate tau protein at distinct sites.
• PKC incorporates approximately 4 mol of phosphate per mol of tau.
• Phosphorylation sites are located within the tubulin-binding domain.
• PKC specifically phosphorylates serine 313 in the tau tubulin-binding region.
• Phosphorylation of tau peptides by PKC reduces their binding affinity to tubulin.

Conclusions:

• Serine 313 is a key phosphorylation site for PKC in the tau tubulin-binding domain.
• PKC-mediated phosphorylation of tau impairs its interaction with tubulin.
• These findings contribute to understanding tauopathies and potential therapeutic targets.