Doctoral thesis (Dissertations and theses)
La 5-phosphatase de phosphoinositides INPP5K régule le développement précoce des lymphocytes B par le biais du contrôle de la structure et de la signalisation du récepteur à l'interleukine 7
Moes, Bastien
2021
 

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Keywords :
B cells; Phosphoinositides; IL-7; INPP5K
Abstract :
[en] INPP5K (Inositol polyphosphate 5-phosphatase K) or SKIP (Skeletal muscle and Kidney enriched Inositol Phosphatase) is an ubiquitously expressed enzyme which belongs to the phosphoinositide 5-phosphatase family. This enzyme hydrolyses both PtdIns(4,5)P2 and PtdIns(3,4,5)P3. Because of the lack of adequate biological tool, the function of Inpp5K in vivo is still poorly characterized,. Indeed, for still unknown reasons, Inpp5K total knock-out mice die during embryonical life at stage E10.5. Since we previously showed that INPP5K mRNA and protein are well expressed in lymphocytes, we generated and crossed Inpp5Kflox/flox mice with VAV-Cre mice, in order to obtain mice deficient for Inpp5K specifically in hematopoietic cells (VAV-CRE). Analysis of these VAV-CRE mice revealed a significant diminution of total B cells in blood, spleen and bone marrow, compared to controls mice. These alterations were associated with a nearly absence of antibody in the blood. Consequentlty, we have analysed early B cell development in bone marrow of VAV-CRE mice. The absence of INPP5K provokes a diversity of complex differences compared with control mice, including a partial blockade of this development between PrePro B (Fr.A) and Early Pro B (Fr.B) stages. These results were confirmed in Inpp5Kflox/flox MB1-CRE (MB1-CRE) where INPP5K is specifically deleted in B cells. To better understand the mechanism behind this partial blockade, the Interleukin 7 receptor (IL7R) pathway, which is essential for initiation and engagement of progenitor cells in the B cell lineage, has been analyzed in VAV-CRE and control mice. In VAV-CRE mice, these analyses revealed at PrePro B and Early Pro B stages a significant decrease in the phosphorylation of JAK1 and JAK3, two kinases that bind to the 2 IL7R chains, as well as of STAT5, their protein target, as compared with control mice. Downstream to STAT5 activation in the IL7R signaling, EBF1 and PAX5 expression was significantly decreased in VAV-CRE mice. This suggests that INPP5K plays an important during the early plasma membrane steps of IL7R activation. This hypothesis is reinforced by the observation of an increased membranous PtdIns(4,5)P2 level in bone marrow VAV-CRE B cells from PrePro B and Early Pro B stages. Confocal microscopy analysis demonstrated that INPP5K inactivation results in an altered formation of GM1+ microdomains which are known to be important for IL7R signaling. Moreover, indirect FRET analysis showed that the absence of INPP5K provokes significant alterations in IL7R dynamic structure both before and after IL7 stimulation. We indeed observed in VAV-CRE bone marrow B cells an increase in the distance between the two extracellular domains of the IL7R, an abnormal mobility of JAK1 and JAK3 kinases and a freeze of the distance between the cytoplasmic tail of IL7Rα chain and the plasma membrane, as compared with control B cells.
Research center :
Giga-Signal Transduction - ULiège
Disciplines :
Immunology & infectious disease
Author, co-author :
Moes, Bastien ;  Université de Liège - ULiège > GIGA Molecular Biology of Diseases - Functional Genetics
Language :
French
Title :
La 5-phosphatase de phosphoinositides INPP5K régule le développement précoce des lymphocytes B par le biais du contrôle de la structure et de la signalisation du récepteur à l'interleukine 7
Alternative titles :
[en] Phosphoinositide 5-phosphatase INPP5K regulates early development of B cells through control of interleukin 7 receptor structure and signaling
Defense date :
22 November 2021
Number of pages :
190
Institution :
ULiège - Université de Liège
Degree :
Docteur en science
Promotor :
Schurmans, Stéphane  ;  Université de Liège - ULiège > GIGA > GIGA Molecular Biology of Diseases - Functional Genetics
President :
Dequiedt, Franck  ;  Université de Liège - ULiège > GIGA > GIGA Molecular Biology of Diseases
Jury member :
Sadzot, Catherine ;  Université de Liège - ULiège > Département des sciences de la vie > Virologie - Immunologie
Desmet, Christophe  ;  Université de Liège - ULiège > GIGA > GIGA I3 - Cellular and Molecular Immunology
Struman, Ingrid  ;  Université de Liège - ULiège > Département des sciences de la vie
Name of the research project :
La 5-phosphatase de phosphoinositides INPP5K régule le développement précoce des lymphocytes B par le biais du contrôle de la structure et de la signalisation du récepteur à l'interleukine 7
Funders :
F.R.S.-FNRS - Fonds de la Recherche Scientifique [BE]
Fonds Léon Fredericq [BE]
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