N-Homocysteinylation Alters Erythropoietin functions

SCHIAPPACASSE, AGUSTINA; MALTANERI, ROMINA; CHAMORRO, MARÍA EUGENIA; WETZLER, DIANA ; NESSE, ALCIRA; VITTORI, DANIELA

Congreso; LXI Reunión Científica de la Sociedad Argentina de Biología (SAIC); LXIV Reunión Anual de la Sociedad Argentina de Inmunología (SAI) y XLVIII Reunión Anual de la Sociedad Argentina de Farmacología; 2016

Erythropoietin(Epo) is a cytokine known by its erythropoietic properties. Despite thesuccesful therapy with recombinant human Epo to overcome the anemia associatedwith different pathologies, a significant number of patients fails to respond.Homocysteine(Hcy) is a sulfur-containing, nonproteinogenic amino acid biosynthesized frommethionine. High levels of homocysteine are associated with cardiovasculardiseases −atherosclerosis and thrombosis−, pregnancy disorders and with variousneurodegenerative disorders. The toxicity of Hcy has been linked with alteredprotein structure due to N-homocysteinylation of lysine residues byreaction with the highly reactive homocysteine thiolactone (HTL). Several serumproteins have been found modifed with HTL. In humans, about 70% of thecirculating HTL is N-linked to proteins, mostly to albumin andhemoglobin. The prevalence of hyperhomocysteinemia is 85% to 100%, when EndStage Renal Disease is developed. In patients on hemodialysis negativeprognosis has been associated with the presence of anemia andhypermocysteinemia. To explain this association we tried to evaluate a possibleinteraction between Epo and HTLThisstudy was conducted to evaluate the effect of N-homocysteinylation onEpo functions and structure. In particular, we studied the erythropoietic andantiapoptotic effect.After incubation with HTL, the proliferative and antiapoptoticproperties of Epo are reduced in a concentration dependentform. Results ofelectrophoresis techniques and the Ellman´s reaction suggested protein N-homocysteinylation.Analysis by circular dichroism and congo red assay confirm that treatment withHTL induces structural alteration of Epo such as changes from alpha to β-sheet structure. Structuralmodifications due to N-homocysteinylation is also confirm by instrinsicfluorescence spectra.