Characterization and physiological roles of interactions between the cellular prion protein and two ligands: its putative 60-66 kDa receptor and laminin / Caracterização e implicações fisiológicas das interações da proteína prion celular com o seu receptor de 60-66 kDa e com a laminina

AUTOR(ES)
DATA DE PUBLICAÇÃO

2000

RESUMO

Prions are defined as proteinaceous infectious particles that mediate the pathogenesis of certain neurodegenerative diseases, in humans and in animals. The prion particle is composed largely, if not entirely, by PrPsc (prion scrapie), a posttranslationaly modified isoform of the cellular host-encoded prion protein (PrPc). PrPc is a glycosylphosphatidylinositol anchored protein that is constitutively expressed by several cell types, mainly on neuronal cell surface. However, the physiological role of this conserved protein remains unclear. ínterested in this normal function of PrPc, our group decided to investigate some interactions that PrPc could be done with other molecules in order to find some clues about it. We have been identified and characterized two interactions that PrPc is involved: with its putative 60-66 kDa receptor and with laminin. In order to better characterize these interactions it was necessary to produce purified PrPc. In this work we will report the expression and the purification of mouse PrPc protein in heterologous system and its use as important tools to investigate the PrPc interactions. A specific cell surface receptor for PrPc has been predicted. Using the concept of complementary hydropathy, our group has identified a 60-66 kDa membrane protein in mouse brain, which seems to be a putative PrPc receptor. ln vitro binding assays using recombinant and native PrPc were able to confirm that the membrane receptor (66 kDa) binds PrPc. Recombinant PrPc was also useful to demonstrate a specific and high affinity (Kd around 10-8M) interaction between PrPc and laminin. In an attempt to map the PrPc binding site in this molecule, laminin peptides with established physiological functions were used in cornpetition binding assays. A peptide derived frorn C-terminal γ-1 chain of mouse laminin, RNIAEIIKDI, was the only one that was able to block the binding of laminin to PrPc, suggesting that this region comprises the PrPc binding site. It was reported in the literature that this peptide simulates the neurite outgrowth and cellular adhesion. In collaboration with Dr. Izquierdos group (UFRGS) we demonstrated that the interaction characterized between this laminins domain and PrPc is involved in the neuritogenesis process, as well as in learning and memory.

ASSUNTO(S)

biologia molecular memória interação protéica prion molecular biology receptor de 60-66 kda laminina 60-66 kda receptor memory prion protein interaction laminin

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