Activation effects of a prion protein fragment [PrP-(106-126)] on human leucocytes

Abstract

Prion-related encephalopathies are characterized by the intracerebral accumulation of an abnormal isoform of the cellular prion protein (PrPC) named scrapie prion protein (PrPSc). The pathological forms of this protein and its cellular precursor are not only expressed in the brain but also, at lower concentrations, in peripheral tissues. We recently showed that a synthetic peptide corresponding to residues 106-126 [PrP-(106-126)] of the human PrP is toxic to neurons and trophic to astrocytes in vitro. Our experiments were aimed at verifying whether PrP-(106-126) and other peptides corresponding to fragments of the amyloid protein purified from brains of patients with Gerstmann-Sträussler-Scheinker disease-namely PrP-(89-106), PrP-(106-114), PrP-(127-147)-were capable of stimulating circulating leucocytes. Native PrP expression in human lymphocytes, monocytes and neutrophils was first confirmed using PCR amplification of total RNA, after reverse transcription, and immunoblot analysis of cell extracts with anti-PrP antibodies. PrP-(106-126), but not the other peptides, increased membrane microviscosity, intracellular Ca2+ concentration and cell migration in circulating leucocytes, and O2-. production in monocytes and neutrophils. Membrane microviscosity was determined by the fluorescence polarization technique, using diphenylhexatriene as a probe, 300 s after the addition of PrP-(106-126) to the cell suspension in the concentration range 5-50 microM. The increase in intracellular Ca2+ elicited by PrP-(106-126) was dose-dependent in the range 5-500 microM. PrP-(106-126) stimulated O2-. production in monocytes and neutrophils in a dose- (10-300 microM) and time-(5-30 min) dependent manner in the presence of 10 microM dihydrocytochalasin B. Both the increase in Ca2+ concentration and the O2-. production were partially sensitive to pertussis toxin. PrP-(106-126) stimulated leucocyte migration in a dose-dependent (30-300 microM) manner and, at the highest concentration used, this migration was comparable with that elicited by 2.5 nM interleukin 8 or 10 nM fMet-Leu-Phe peptide.

Molecular determinants of the physicochemical properties of a critical prion protein region comprising residues 106–126

“…It is noteworthy that the neurotoxicity of the peptide requires the expression of endogenous PrP, which is consistent with the observation that neuronal death in scrapie infection in i o is dependent on PrP C synthesis [16,17]. It also increases the membrane microviscosity of a variety of cells, including neurons and astrocytes [18,19]. PrP106-126 shows a remarkable conformational polymorphism, acquiring different secondary structures in different environments [15] ; nevertheless, it tends to adopt a β-sheet conformation in buffered solutions and aggregates into amyloid fibrils that are partly resistant to digestion with protease.…”

The normal cellular prion protein is strongly expressed by myeloid dendritic cells

“…Indeed, in mice, PrP C has been indirectly linked to a role in T-cell activation by observations that peptides from PrP C may directly induce T-cell activation. 37,38 Although there have been no detailed reports of immune function in PrP CϪ/Ϫ knockout mice, in the absence of PrP C concanavalin-A-induced activation of T cells is reduced. 39 DCs are believed to be central to the ability of concanavalin-A to activate T cells.…”

All-trans retinoic acid down-regulates prion protein expression independently of granulocyte maturation

“…14,[16][17][18][19] The presence of PrPc in granulocytes is still unclear. 39,45 These conflicting results can be explained by the sensitivity of the assays used. Diomede and colleagues 45 used immunoprecipitation and reverse transcription-polymerase chain reaction (RT-PCR) assays to detect PrPc expression in neutrophils.…”

“…39,45 These conflicting results can be explained by the sensitivity of the assays used. Diomede and colleagues 45 used immunoprecipitation and reverse transcription-polymerase chain reaction (RT-PCR) assays to detect PrPc expression in neutrophils. These assays enable enrichment of prion mRNA and protein.…”