Dataset Information

Fc?RI Dynamics Are Regulated by GSK-3 and PKC? During Cytokine Mediated Inside-Out Signaling.

ABSTRACT: IgA binding to Fc?RI (CD89) is rapidly enhanced by cytokine induced inside-out signaling. Dephosphorylation of serine 263 in the intracellular tail of Fc?RI by PP2A and PI3K activation are instrumental in this process. To further investigate these signaling pathways, we targeted downstream kinases of PI3K. Our experiments revealed that PI3K activates PKC?, which subsequently inhibits GSK-3, a constitutively active kinase in resting cells and found here to be associated with Fc?RI. We propose that GSK-3 maintains Fc?RI in an inactive state at homeostatic conditions. Upon cytokine stimulation, GSK-3 is inactivated through a PI3K-PKC? pathway, preventing the maintenance of phosphorylated inactive Fc?RI. The concomitantly activated PP2A is then able to dephosphorylate and activate Fc?RI. Moreover, FRAP and FLIP studies showed that Fc?RI activation coincides with an increased mobile fraction of the receptor. This can enhance Fc?RI valency and contribute to stronger avidity for IgA immune complexes. This tightly regulated inside-out signaling pathway allows leukocytes to respond rapidly and efficiently to their environment and could be exploited to enhance the efficacy of future IgA therapeutics.

SUBMITTER: Ten Broeke T

PROVIDER: S-EPMC6365424 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Publications

FcαRI Dynamics Are Regulated by GSK-3 and PKCζ During Cytokine Mediated Inside-Out Signaling.

Ten Broeke Toine T Honing Henk H Brandsma Arianne M AM Jacobino Shamir S Bakema Jantine E JE Kanters Deon D van der Linden Jan A M JAM Bracke Madelon M Koenderman Leo L Leusen Jeanette H W JHW

Frontiers in immunology 20190131

IgA binding to FcαRI (CD89) is rapidly enhanced by cytokine induced inside-out signaling. Dephosphorylation of serine 263 in the intracellular tail of FcαRI by PP2A and PI3K activation are instrumental in this process. To further investigate these signaling pathways, we targeted downstream kinases of PI3K. Our experiments revealed that PI3K activates PKCζ, which subsequently inhibits GSK-3, a constitutively active kinase in resting cells and found here to be associated with FcαRI. We propose tha ...[more]

PMID: 30766540

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Project description:BackgroundDuring transendothelial migration, leukocytes use adhesion molecules, such as ICAM-1, to adhere to the endothelium. ICAM-1 is a dynamic molecule that is localized in the apical membrane of the endothelium and clusters upon binding to leukocytes. However, not much is known about the regulation of ICAM-1 clustering and whether membrane dynamics are linked to the ability of ICAM-1 to cluster and bind leukocyte integrins. Therefore, we studied the dynamics of endothelial ICAM-1 under non-clustered and clustered conditions.Principal findingsDetailed scanning electron and fluorescent microscopy showed that the apical surface of endothelial cells constitutively forms small filopodia-like protrusions that are positive for ICAM-1 and freely move within the lateral plane of the membrane. Clustering of ICAM-1, using anti-ICAM-1 antibody-coated beads, efficiently and rapidly recruits ICAM-1. Using fluorescence recovery after photo-bleaching (FRAP), we found that clustering increased the immobile fraction of ICAM-1, compared to non-clustered ICAM-1. This shift required the intracellular portion of ICAM-1. Moreover, biochemical assays showed that ICAM-1 clustering recruited beta-actin and filamin. Cytochalasin B, which interferes with actin polymerization, delayed the clustering of ICAM-1. In addition, we could show that cytochalasin B decreased the immobile fraction of clustered ICAM-1-GFP, but had no effect on non-clustered ICAM-1. Also, the motor protein myosin-II is recruited to ICAM-1 adhesion sites and its inhibition increased the immobile fraction of both non-clustered and clustered ICAM-1. Finally, blocking Rac1 activation, the formation of lipid rafts, myosin-II activity or actin polymerization, but not Src, reduced the adhesive function of ICAM-1, tested under physiological flow conditions.ConclusionsTogether, these findings indicate that ICAM-1 clustering is regulated in an inside-out fashion through the actin cytoskeleton. Overall, these data indicate that signaling events within the endothelium are required for efficient ICAM-1-mediated leukocyte adhesion.

Dataset Information

Fc?RI Dynamics Are Regulated by GSK-3 and PKC? During Cytokine Mediated Inside-Out Signaling.

Publications

FcαRI Dynamics Are Regulated by GSK-3 and PKCζ During Cytokine Mediated Inside-Out Signaling.

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