TY - JOUR
T1 - Btk regulation in human and mouse B cells via protein kinase C phosphorylation of IBtkγ
AU - Janda, Elzbieta
AU - Palmieri, Camillo
AU - Pisano, Antonio
AU - Pontoriero, Marilena
AU - Iaccino, Enrico
AU - Falcone, Cristina
AU - Fiume, Giuseppe
AU - Gaspari, Marco
AU - Nevolo, Maria
AU - Di Salle, Emanuela
AU - Rossi, Annalisa
AU - De Laurentiis, Annamaria
AU - Greco, Adelaide
AU - Di Napoli, Daniele
AU - Verheij, Elwin
AU - Britti, Domenico
AU - Lavecchia, Luca
AU - Quinto, Ileana
AU - Scala, Giuseppe
PY - 2011/6/16
Y1 - 2011/6/16
N2 - The inhibitor of Bruton tyrosine kinase γ (IBtkγ) is a negative regulator of the Bruton tyrosine kinase (Btk), which plays a major role in B-cell differentiation; however, the mechanisms of IBtkγ-mediated regulation of Btk are unknown. Here we report that B-cell receptor (BCR) triggering caused serine-phosphorylation of IBtkγ at protein kinase C consensus sites and dissociation from Btk. By liquid chromatography and mass-mass spectrometry and functional analysis, we identified IBtkγ-S87 and -S90 as the critical amino acid residues that regulate the IBtkγ binding affinity to Btk. Consistently, the mutants IBtkγ carrying S87A and S90A mutations bound constitutively to Btk and down-regulated Ca2+ fluxes and NF-κB activation on BCR triggering. Accordingly, spleen B cells from Ibtkγ-/- mice showed an increased activation of Btk, as evaluated by Y551-phosphorylation and sustained Ca2+ mobilization on BCR engagement. These findings identify a novel pathway of Btk regulation via protein kinase C phosphorylation of IBtkγ.
AB - The inhibitor of Bruton tyrosine kinase γ (IBtkγ) is a negative regulator of the Bruton tyrosine kinase (Btk), which plays a major role in B-cell differentiation; however, the mechanisms of IBtkγ-mediated regulation of Btk are unknown. Here we report that B-cell receptor (BCR) triggering caused serine-phosphorylation of IBtkγ at protein kinase C consensus sites and dissociation from Btk. By liquid chromatography and mass-mass spectrometry and functional analysis, we identified IBtkγ-S87 and -S90 as the critical amino acid residues that regulate the IBtkγ binding affinity to Btk. Consistently, the mutants IBtkγ carrying S87A and S90A mutations bound constitutively to Btk and down-regulated Ca2+ fluxes and NF-κB activation on BCR triggering. Accordingly, spleen B cells from Ibtkγ-/- mice showed an increased activation of Btk, as evaluated by Y551-phosphorylation and sustained Ca2+ mobilization on BCR engagement. These findings identify a novel pathway of Btk regulation via protein kinase C phosphorylation of IBtkγ.
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U2 - 10.1182/blood-2010-09-308080
DO - 10.1182/blood-2010-09-308080
M3 - Article
C2 - 21482705
AN - SCOPUS:79959257186
VL - 117
SP - 6520
EP - 6531
JO - Blood
JF - Blood
SN - 0006-4971
IS - 24
ER -