Affiliations: Instituto de Bioquímica, Unidade Biologia Microvascular e Inflamação, Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal
Note: [] Corresponding author: Sofia de Oliveira, Instituto de Bioquímica, Unidade Biologia Microvascular e Inflamação, Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, 1649-028 Lisboa, Portugal. Tel.: +351 21 799 94 78; Fax: +351 21 799 94 77; E-mail: sloliveira@fm.ul.pt.
Abstract: The interactions between membrane, peripheral and cytoskeleton proteins are responsible for the maintenance of erythrocyte deformability (EEI) and some of these interactions are modulated by PKC activity. Protein band 3 of the erythrocyte membrane is phosphorylated by phosphotyrosine kinases (PTK) and dephosphorylated by phosphotyrosine phosphatase (PTP). It was previously described by us a signal transduction mechanism that describes a possible pathway connecting an erythrocyte external membrane protein, acetylcholinesterase (AChE), with protein band 3. So how does PKC activity modulate EEI when protein band 3 is phosphorylated or dephosphorylated in absence or presence of AChE effectors? To answer this we used phorbol 12-myristate 13-acetate (PMA) as an activator and chelerythrine chloride as inhibitor of PKC and also band 3 modulators of band 3 phosphorylation degree, in presence and absence of AChE effectors in order to measure in whole blood samples EEI. Our results showed that erythrocyte deformability was significantly (i) decreased by inhibition of PKC, in absence and presence of AChE inhibitor velnacrine (ii) increased with PMA in absence and presence of ACh and (iii) decreased in presence of calpeptin in absence and presence of either chelerythrine or PMA. These results establish dependence between cytoskeleton proteins, PKC activity, band 3 phosphorylation degrees and EEI. Better understanding of those proteins interactions on transduction mechanisms might trigger possible targets for drug action that would modulate EEI.
Keywords: Erythrocyte protein band 3, protein tyrosine kinases, phosphotyrosine phosphatase, acetylcholinesterase, cytoskeleton, protein kinase C
