title: Oxidation-induced structural changes of ceruloplasmin foster NGR motif deamidation that promotes integrin binding and signaling.
abstract: Asparagine deamidation occurs spontaneously in proteins during aging; deamidation of Asn-Gly-Arg (NGR) sites can lead to the formation of isoAsp-Gly-Arg (isoDGR), a motif that can recognize the RGD-binding site of integrins. Ceruloplasmin (Cp), a ferroxidase present in the cerebrospinal fluid (CSF), contains two NGR sites in its sequence: one exposed on the protein surface ((568)NGR) and the other buried in the tertiary structure ((962)NGR). Considering that Cp can undergo oxidative modifications in the CSF of neurodegenerative diseases, we investigated the effect of oxidation on the deamidation of both NGR motifs and, consequently, on the acquisition of integrin binding properties. We observed that the exposed (568)NGR site can deamidate under conditions mimicking accelerated Asn aging. In contrast, the hidden (962)NGR site can deamidate exclusively when aging occurs under oxidative conditions, suggesting that oxidation-induced structural changes foster deamidation at this site. NGR deamidation in Cp was associated with gain of integrin-binding function, intracellular signaling, and cell pro-adhesive activity. Finally, Cp aging in the CSF from Alzheimer disease patients, but not in control CSF, causes Cp deamidation with gain of integrin-binding function, suggesting that this transition might also occur in pathological conditions. In conclusion, both Cp NGR sites can deamidate during aging under oxidative conditions, likely as a consequence of oxidative-induced structural changes, thereby promoting a gain of function in integrin binding, signaling, and cell adhesion.
authors.affiliation: From the Proteome Biochemistry.
authors.forename: Marco
authors.initials: M
authors.lastname: Barbariga
authors.forename: Flavio
authors.initials: F
authors.lastname: Curnis
authors.forename: Andrea
authors.initials: A
authors.lastname: Spitaleri
authors.forename: Annapaola
authors.initials: A
authors.lastname: Andolfo
authors.forename: Chiara
authors.initials: C
authors.lastname: Zucchelli
authors.forename: Massimo
authors.initials: M
authors.lastname: Lazzaro
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Magnani
authors.forename: Giovanna
authors.initials: G
authors.lastname: Musco
authors.forename: Angelo
authors.initials: A
authors.lastname: Corti
authors.forename: Massimo
authors.initials: M
authors.lastname: Alessio
mesh_terms: D000544:Alzheimer Disease / Q000134:cerebrospinal fluid / Q000235:genetics; D020816:Amino Acid Motifs; D002448:Cell Adhesion / Q000235:genetics; D045744:Cell Line, Tumor; D002570:Ceruloplasmin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D016023:Integrins / Q000235:genetics / Q000378:metabolism; D010084:Oxidation-Reduction; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D015398:Signal Transduction
chemical_list: D016023:Integrins; D002570:Ceruloplasmin
keywords: Alzheimer Disease; Ceruloplasmin; Integrins; NGR Motif; Oxidative Stress; Protein Deamidation; Protein Misfolding; Structural Biology; isoNGR Motif