Autophosphorylation of Ser(428) of EhC2PK Plays a Critical Role in Regulating Erythrophagocytosis in the Parasite Entamoeba histolytica

The protozoan parasite Entamoeba histolytica can invade both intestinal and extra intestinal tissues resulting in amoebiasis. During the process of invasion E. histolytica ingests red blood and host cells using phagocytic processes. Though phagocytosis is considered to be a key virulence determinant, the mechanism is not very well understood in E. histolytica. We have recently demonstrated that a novel C2 domain-containing protein kinase, EhC2PK is involved in the initiation of erythrophagocytosis. Because cells overexpressing the kinase-dead mutant of EhC2PK displayed a reduction in erythrophagocytosis, it appears that kinase activity is necessary for initiation. Biochemical analysis showed that EhC2PK is an unusual Mn2+-dependent serine kinase. It has a trans-autophosphorylated site at Ser(428) as revealed by mass spectrometric and biochemical analysis. The autophosphorylation defective mutants (S428A, KD Delta C) showed a reduction in auto and substrate phosphorylation. Time kinetics of in vitro kinase activity suggested two phases, an initial short slow phase followed by a rapid phase for wild type protein, whereas mutations in the autophosphorylation sites that cause defect (S428A) or conferred phosphomimetic property (S428E) displayed no distinct phases, suggesting that autophosphorylation may be controlling kinase activity through an autocatalytic mechanism. A reduction and delay in erythrophagocytosis was observed in E. histolytica cells overexpressing S428A and KD Delta C proteins. These results indicate that enrichment of EhC2PK at the site of phagocytosis enhances the rate of trans-autophosphorylation, thereby increasing kinase activity and regulating the initiation of erythrophagocytosis in E. histolytica.

Les diplômés – no 428, printemps 2015

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Resolución 428(XIX): Comercio agrícola y seguridad alimentaria = Resolution 428(XIX): Agricultural trade and food security = Résolution 428(XIX): Commerce agricole et sécurité alimentaire

Publicado separadamete en cada idioma

Atropelamento de vertebrados nas rodovias MG-428 e SP-334 com análise dos fatores condicionantes e valoração econômica da fauna

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Na 50 Nachlass Arthur Schopenhauer - 'Schopenhauer-Archiv', 428 - Zitatensammlung mit dem Titel: "Platonica"

2 Seiten

Ms.Ff.F.Stoltze 3. 428 - Brief von Friedrich Stoltze an Friedrich Stoltze

Familie, Bälle, Gelegenheitsarbeiten, Hermann Stoltze

Ana María Barrenechea y colaboradores. Epistolario inédito Sarmiento - Frías Instituto de Filología y Literaturas Hispánicas 'Dr. Amado Alonso', Facultad de Filosofía y Letras, Universidad de Buenos Aires, 1997, 428 páginas

Fil: Pastormerlo, Sergio Carlos. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

Ana María Barrenechea y colaboradores. Epistolario inédito Sarmiento - Frías Instituto de Filología y Literaturas Hispánicas 'Dr. Amado Alonso', Facultad de Filosofía y Letras, Universidad de Buenos Aires, 1997, 428 páginas

Fil: Pastormerlo, Sergio Carlos. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.