Expression and Phosphorylation of Protein Kinase C Isoforms in Aβ 1–42 Activated T Lymphocytes from Alzheimer's Disease

Abstract

The protein kinase C (PKC) family of enzymes is a regulator of transmembrane signal transduction. There is evidence demonstrating altered activity of some PKC isoforms (PKC-α, PKC-δ and PKC-ζ) in the neurons of brains of Alzheimer's Disease (AD) sufferers, but little is known about their involvement in the intracellular machinery of amyloid β protein-reactive T lymphocytes in AD. By applying a modified “split-well culture system” for Aβ_1–42 reactivity, we carried out flow cytometry analysis and biochemical investigations on the possible involvement of PKC-α, PKC-δ and PKC-ζ in the signalling system activated in Aβ-reactive T cells purified from peripheral blood mononucleate cells (PBMC) from healthy subjects and patients with AD. Flow cytometry analysis of Aβ_1–42 activated T lymphocytes in the majority of AD patients highlighted a distinct cellular cluster highly expressing phospho-PKC-δ (P-PKC-δ), while most full-blown AD patients highly expressed two distinct P-PKC-δ and phospho-PKC-ζ (P-PKC-ζ) bright sub-populations. The same investigation performed in freshly purified peripheral T lymphocytes, did not highlight any subpopulation, suggesting that the detection of P-PKC-δ and P-PKC-ζ bright subpopulations is specifically linked to Aβ_1–42 activated T lymphocytes. The data presented here, therefore, suggest possible novel hallmarks to discriminate between healthy elderly subjects and beginning or full-blown Alzheimer's Disease patients.