The adaptor molecule CIN85 regulates Syk tyrosine kinase level by activating the ubiquitin-proteasome degradation pathway.
Triggering of mast cells and basophils by IgE and Ag initiates a cascade of biochemical events that lead to cell degranulation and the release of allergic mediators. Receptor aggregation also induces a series of biochemical events capable of limiting FcepsilonRI-triggered signals and functional responses. Relevant to this, we have recently demonstrated that Cbl-interacting 85-kDa protein (CIN85), a multiadaptor protein mainly involved in the process of endocytosis and vesicle trafficking, regulates the Ag-dependent endocytosis of the IgE receptor, with consequent impairment of FcepsilonRI-mediated cell degranulation. The purpose of this study was to further investigate whether CIN85 could alter the FcepsilonRI-mediated signaling by affecting the activity and/or expression of molecules directly implicated in signal propagation. We found that CIN85 overexpression inhibits the FcepsilonRI-induced tyrosine phosphorylation of phospholipase Cgamma, thus altering calcium mobilization. This functional defect is associated with a substantial decrease of Syk protein levels, which are restored by the use of selective proteasome inhibitors, and it is mainly due to the action of the ubiquitin ligase c-Cbl. Furthermore, coimmunoprecipitation experiments demonstrate that CIN85 overexpression limits the ability of Cbl to bind suppressor of TCR signaling 1 (Sts1), a negative regulator of Cbl functions, while CIN85 knockdown favors the formation of Cbl/Sts1 complexes. Altogether, our findings support a new role for CIN85 in regulating Syk protein levels in RBL-2H3 cells through the activation of the ubiquitin-proteasome pathway and provide a mechanism for this regulation involving c-Cbl ligase activity.
Department of Experimental Medicine, Institute Pasteur-Fondazione Cenci Bolognetti, University La Sapienza, Rome, Italy.
Giovanna
G
Peruzzi
Rosa
R
Molfetta
Francesca
F
Gasparrini
Laura
L
Vian
Stefania
S
Morrone
Mario
M
Piccoli
Luigi
L
Frati
Angela
A
Santoni
Rossella
R
Paolini
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D000818:Animals; D000941:Antigens / Q000276:immunology / Q000378:metabolism; D001491:Basophils / Q000276:immunology / Q000378:metabolism; D020013:Calcium Signaling / Q000235:genetics / Q000276:immunology; D015550:Cell Degranulation / Q000235:genetics / Q000276:immunology; D002460:Cell Line; D004705:Endocytosis / Q000235:genetics / Q000276:immunology; D015870:Gene Expression; D006801:Humans; D007070:Immunoglobulin A / Q000276:immunology / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D008407:Mast Cells / Q000276:immunology / Q000378:metabolism; D009363:Neoplasm Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D051966:Phospholipase C gamma; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D050721:Proto-Oncogene Proteins c-cbl / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D051381:Rats; D011948:Receptors, Antigen, T-Cell / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D017455:Receptors, IgE / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D000072377:Syk Kinase; D025801:Ubiquitin / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000276:immunology / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D000941:Antigens; D007070:Immunoglobulin A; D047908:Intracellular Signaling Peptides and Proteins; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D011948:Receptors, Antigen, T-Cell; D017455:Receptors, IgE; C433810:SH3KBP1 protein, human; C411889:Sh3kbp1 protein, rat; D025801:Ubiquitin; D050721:Proto-Oncogene Proteins c-cbl; D044767:Ubiquitin-Protein Ligases; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase; C000606898:Syk protein, rat; D051966:Phospholipase C gamma; D046988:Proteasome Endopeptidase Complex; C067419:CBL protein, human