RESUMO
The quality of the adaptive immune response depends on the differentiation of distinct CD4(+) helper T cell subsets, and the magnitude of an immune response is controlled by CD4(+)Foxp3(+) regulatory T cells (Treg cells). However, how a tissue- and cell type-specific suppressor program of Treg cells is mechanistically orchestrated has remained largely unexplored. Through the use of Treg cell-specific gene targeting, we found that the suppression of allergic immune responses in the lungs mediated by T helper type 2 (TH2) cells was dependent on the activity of the protein kinase CK2. Genetic ablation of the ß-subunit of CK2 specifically in Treg cells resulted in the proliferation of a hitherto-unexplored ILT3(+) Treg cell subpopulation that was unable to control the maturation of IRF4(+)PD-L2(+) dendritic cells required for the development of TH2 responses in vivo.
Assuntos
Caseína Quinase II/imunologia , Linfócitos T Reguladores/imunologia , Células Th2/imunologia , Animais , Linfócitos T CD4-Positivos/enzimologia , Linfócitos T CD4-Positivos/imunologia , Diferenciação Celular/imunologia , Processos de Crescimento Celular/imunologia , Linhagem Celular , Células Dendríticas/enzimologia , Células Dendríticas/imunologia , Fatores de Transcrição Forkhead/imunologia , Humanos , Hipersensibilidade/sangue , Hipersensibilidade/imunologia , Fatores Reguladores de Interferon/imunologia , Leucócitos Mononucleares/imunologia , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Receptores de Superfície Celular/imunologia , Linfócitos T Reguladores/enzimologia , Células Th2/enzimologiaRESUMO
Mucin expression and glycosylation patterns on cancer cells differ markedly from healthy cells. Mucin 1 (MUC1) is overexpressed in several solid tumors and presents high levels of aberrant, truncated O-glycans (e.g., Tn antigen). Dendritic cells (DCs) express lectins that bind to these tumor-associated carbohydrate antigens (TACAs) to modulate immune responses. Selectively targeting these receptors with synthetic TACAs is a promising strategy to develop anticancer vaccines and to overcome TACA tolerance. In this work, we prepared, via a solid phase peptide synthesis approach, a modular tripartite vaccine candidate, incorporating a high-affinity glycocluster based on a tetraphenylethylene scaffold, to target the macrophage galactose-type lectin (MGL) on antigen presenting cells. MGL is a C-type lectin receptor that binds Tn antigens and can route them to human leukocyte antigen class II or I, making it an attractive target for anticancer vaccines. Conjugation of the glycocluster to a library of MUC1 glycopeptides bearing the Tn antigen is shown to promote uptake and recognition of the TACA by DCs via MGL. In vivo testing revealed that immunization with the newly designed vaccine construct bearing the GalNAc glycocluster induced a higher titer of anti-Tn-MUC1 antibodies compared to the TACAs alone. Additionally, the antibodies obtained bind a library of tumor-associated saccharide structures on MUC1 and MUC1-positive breast cancer cells. Conjugation of a high-affinity ligand for MGL to tumor-associated MUC1 glycopeptide antigens has a synergistic impact on antibody production.
Assuntos
Mucina-1 , Vacinas , Humanos , Mucina-1/química , Galactose/metabolismo , Glicopeptídeos/química , Antígenos Glicosídicos Associados a Tumores/química , Lectinas Tipo C/metabolismo , Células Dendríticas , Macrófagos/metabolismoRESUMO
T helper (Th)17 cells represent a unique subset of CD4+ T cells and are vital for clearance of extracellular pathogens including bacteria and fungi. However, Th17 cells are also involved in orchestrating autoimmunity. By employing quantitative surface proteomics, we found that the evolutionarily conserved prohibitins (PHB1/2) are highly expressed on the surface of both murine and human Th17 cells. Increased expression of PHBs at the cell surface contributed to enhanced CRAF/MAPK activation in Th17 cells. Targeting surface-expressed PHBs on Th17 cells with ligands such as Vi polysaccharide (Typhim vaccine) inhibited CRAF-MAPK pathway, reduced interleukin (IL)-17 expression and ameliorated disease pathology with an increase in FOXP3+-expressing Tregs in an animal model for multiple sclerosis (MS). Interestingly, we detected a CD4+ T cell population with high PHB1 surface expression in blood samples from MS patients in comparison with age- and sex-matched healthy subjects. Our observations suggest a pivotal role for the PHB-CRAF-MAPK signalling axis in regulating the polarization and pathogenicity of Th17 cells and unveil druggable targets in autoimmune disorders such as MS.
Assuntos
Autoimunidade , Esclerose Múltipla/imunologia , Proteínas Repressoras/imunologia , Transdução de Sinais/imunologia , Células Th17/imunologia , Animais , MAP Quinases Reguladas por Sinal Extracelular/imunologia , Fatores de Transcrição Forkhead/imunologia , Células HeLa , Humanos , Camundongos , Esclerose Múltipla/patologia , Proibitinas , Vacinas Antirrickéttsia/farmacologia , Linfócitos T Reguladores/imunologia , Linfócitos T Reguladores/patologia , Células Th17/patologiaRESUMO
The RAS oncogenes are frequently mutated in human cancers and among the three isoforms (KRAS, HRAS and NRAS), KRAS is the most frequently mutated oncogene. Here, we demonstrate that a subset of flavaglines, a class of natural anti-tumour drugs and chemical ligands of prohibitins, inhibit RAS GTP loading and oncogene activation in cells at nanomolar concentrations. Treatment with rocaglamide, the first discovered flavagline, inhibited the nanoclustering of KRAS, but not HRAS and NRAS, at specific phospholipid-enriched plasma membrane domains. We further demonstrate that plasma membrane-associated prohibitins directly interact with KRAS, phosphatidylserine and phosphatidic acid, and these interactions are disrupted by rocaglamide but not by the structurally related flavagline FL1. Depletion of prohibitin-1 phenocopied the rocaglamide-mediated effects on KRAS activation and stability. We also demonstrate that flavaglines inhibit the oncogenic growth of KRAS-mutated cells and that treatment with rocaglamide reduces non-small-cell lung carcinoma (NSCLC) tumour nodules in autochthonous KRAS-driven mouse models without severe side effects. Our data suggest that it will be promising to further develop flavagline derivatives as specific KRAS inhibitors for clinical applications.
Assuntos
Carcinoma Pulmonar de Células não Pequenas , Neoplasias Pulmonares , Carcinoma Pulmonar de Células não Pequenas/tratamento farmacológico , Carcinoma Pulmonar de Células não Pequenas/genética , Humanos , Neoplasias Pulmonares/tratamento farmacológico , Neoplasias Pulmonares/genética , Mutação/genética , Oncogenes , Proteínas Proto-Oncogênicas p21(ras)/genética , Transdução de SinaisRESUMO
Over the last three decades, the scaffold proteins prohibitins-1 and -2 (PHB1/2) have emerged as key signaling proteins regulating a myriad of signaling pathways in health and diseases. Small molecules targeting PHBs display promising effects against cancers, osteoporosis, inflammatory, cardiac and neurodegenerative diseases. This review provides an updated overview of the various classes of PHB ligands, with an emphasis on their mechanism of action and therapeutic potential. We also describe how these ligands have been used to explore PHB signaling in different physiological and pathological settings.
Assuntos
Cardiopatias/patologia , Ligantes , Neoplasias/terapia , Doenças do Sistema Nervoso/terapia , Osteoporose/terapia , Proteínas Repressoras/metabolismo , Expressão Gênica , Cardiopatias/metabolismo , Cardiopatias/terapia , Humanos , Neoplasias/metabolismo , Neoplasias/patologia , Doenças do Sistema Nervoso/metabolismo , Doenças do Sistema Nervoso/patologia , Osteoporose/metabolismo , Osteoporose/patologia , Proibitinas , Processamento de Proteína Pós-Traducional , Proteínas Repressoras/química , Proteínas Repressoras/genética , Transdução de SinaisRESUMO
A modular route to prepare functional self-assembling dendritic peptide amphiphiles decorated with mannosides, to effectively target antigen-presenting cells, such as macrophages, is reported. The monomeric building blocks were equipped with tetra(ethylene glycol)s (TEGs) or labeled with a Cy3 fluorescent probe. Experiments on the uptake of the multifunctional supramolecular particles into murine macrophages (Mφs) were monitored by confocal microscopy and fluorescence-activated cell sorting. Mannose-decorated supramolecular polymers trigger a significantly higher cellular uptake and distribution, relative to TEG carrying bare polymers. No cytotoxicity or negative impact on cytokine production of the treated Mφs was observed, which emphasized their biocompatibility. The modular nature of the multicomponent supramolecular polymer coassembly protocol is a promising platform to develop fully synthetic multifunctional vaccines, for example, in cancer immunotherapy.
Assuntos
Células Apresentadoras de Antígenos/metabolismo , Dendrímeros/metabolismo , Manosídeos/metabolismo , Peptídeos/metabolismo , Tensoativos/metabolismo , Animais , Transporte Biológico , Carbocianinas/química , Carbocianinas/metabolismo , Células Cultivadas , Dendrímeros/química , Corantes Fluorescentes/química , Corantes Fluorescentes/metabolismo , Macrófagos/metabolismo , Manosídeos/química , Camundongos , Microscopia Confocal , Modelos Moleculares , Peptídeos/química , Polietilenoglicóis/química , Polietilenoglicóis/metabolismo , Tensoativos/químicaRESUMO
The voltage-gated potassium channel 1.6 (Kv1.6) plays a vital role in ocular neurovascular beds and exerts its modulatory functions via interaction with other proteins. However, the interactome and their potential roles remain unknown. Here, the global proteome landscape of the ophthalmic artery (OA) and neuroretina was mapped, followed by the determination of Kv1.6 interactome and validation of its functionality and cellular localization. Microfluorimetric analysis of intracellular [K+] and Western blot validated the native functionality and cellular expression of the recombinant Kv1.6 channel protein. A total of 54, 9 and 28 Kv1.6-interacting proteins were identified in the mouse OA and, retina of mouse and rat, respectively. The Kv1.6-protein partners in the OA, namely actin cytoplasmic 2, alpha-2-macroglobulin and apolipoprotein A-I, were implicated in the maintenance of blood vessel integrity by regulating integrin-mediated adhesion to extracellular matrix and Ca2+ flux. Many retinal protein interactors, particularly the ADP/ATP translocase 2 and cytoskeleton protein tubulin, were involved in endoplasmic reticulum stress response and cell viability. Three common interactors were found in all samples comprising heat shock cognate 71 kDa protein, Ig heavy constant gamma 1 and Kv1.6 channel. This foremost in-depth investigation enriched and identified the elusive Kv1.6 channel and, elucidated its complex interactome.
Assuntos
Canais de Potássio de Abertura Dependente da Tensão da Membrana , Camundongos , Ratos , Animais , Canais de Potássio de Abertura Dependente da Tensão da Membrana/genética , Canais de Potássio/metabolismo , Proteoma/metabolismo , Artéria Oftálmica/química , Artéria Oftálmica/metabolismo , Citoplasma/metabolismoRESUMO
Previously we demonstrated that prohibitin-1 and -2 (prohibitins) were expressed on the surface of T cell leukemia cell lines and activated T lymphocytes. In the present study, we found that prohibitins play a role as counter receptors for Siglec-9 expressed on macrophages and dendritic cells. Siglec-9 bound to prohibitins in a sialic acid-independent manner. Mutated Siglec-9 with Arg(120) changed to Ala lost the binding activity, suggesting a specific ionic peptide-peptide interaction. Phosphorylation of ERK1/2 in Jurkat cells on treatment with anti-CD3 antibody immobilized beads was markedly diminished on treatment with anti-CD3 antibody and Siglec-9 co-immobilized beads, indicating that engagement of prohibitins with Siglec-9 inhibits ERK1/2 phosphorylation. Phosphorylation of c-Raf was also reduced, maybe due to inhibition of the c-Raf-prohibitin interaction by Siglec-9 ligation. In parallel with inhibition of the ERK cascade, IL-2 production was markedly decreased in Jurkat cells. Thus, this interaction may be a useful immunotherapeutic target.
Assuntos
Sistema de Sinalização das MAP Quinases , Receptores de Antígenos de Linfócitos T/metabolismo , Proteínas Repressoras/metabolismo , Lectinas Semelhantes a Imunoglobulina de Ligação ao Ácido Siálico/metabolismo , Animais , Complexo CD3/metabolismo , Células CHO , Cricetinae , Humanos , Células Jurkat , Ligantes , Ativação Linfocitária , Proteína Quinase 1 Ativada por Mitógeno/metabolismo , Fosforilação , Proibitinas , Ligação Proteica , RNA Interferente Pequeno/genética , RNA Interferente Pequeno/metabolismo , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Lectinas Semelhantes a Imunoglobulina de Ligação ao Ácido Siálico/genética , TransfecçãoRESUMO
Prohibitins (prohibitin-1 and -2) comprise a family of highly conserved proteins that are mainly localized to mitochondria. Recent studies showed that prohibitins are up-regulated upon T cell activation and play an essential role in maintaining mitochondrial homeostasis. In the present study, we found that a considerable proportion of prohibitin-1 and -2 induced in response to T cell activation was expressed on the surface of activated T cells. When mouse and human T cells were stimulated with PMA and ionomycin, prohibitins expressed on the cell surface were increased significantly, peaking at 48 h after stimulation. Stimulation of mouse T cells with anti-CD3 and anti-CD28 antibodies also remarkably induced the cell surface expression of prohibitins. Their expression on the cell surface was also detected in T cell leukemia cells such as Jurkat cells. In Jurkat cells, prohibitin-1 and -2 were co-localized with CD3 on the cell surface, and anti-CD3 antibody-induced signaling, the MAP kinase cascade, was inhibited on treatment with protein A magnetic beads co-conjugated with anti-CD3 antibody and anti-prohibitin-1 or anti-prohibitin-2 antibody. These results suggest that prohibitins expressed on the surface of activated T cells are involved in the T cell receptor-mediated signaling cascade.
Assuntos
Membrana Celular/imunologia , Ativação Linfocitária , Proteínas Repressoras/biossíntese , Linfócitos T/imunologia , Animais , Anticorpos , Feminino , Humanos , Células Jurkat , Camundongos , Camundongos Endogâmicos BALB C , Proibitinas , Proteínas Repressoras/antagonistas & inibidores , Proteínas Repressoras/imunologiaRESUMO
Fluorizoline is a cytotoxic trifluorothiazoline that targets the scaffold proteins prohibitins-1 and -2 (PHB1/2) to inhibit the kinase C-RAF and promote the expression of the cyclin-dependent kinase inhibitor p21 to induce cancer cell death. In melanocytes, fluorizoline also induces the synthesis of melanin. Herein we report the first structural requirement of fluorizoline analogues for these activities. We identified in particular some compounds that display enhanced anti-C-RAF and anti-MEK activities, and a higher cytotoxicity in HeLa cells compared to fluorizoline. These results provide a foundation for further optimization of PHB ligands for the treatment of cancers. We also discovered an analogue of fluorizoline that displays pharmacological effects opposed to those of fluorizoline and that can be used as a chemical tool to explore PHB signaling in cancers and other diseases.
Assuntos
Apoptose , Proibitinas , Inibidor de Quinase Dependente de Ciclina p21/metabolismo , Células HeLa , Humanos , Ligantes , Melaninas/metabolismo , Proteínas Serina-Treonina Quinases , Proteínas Proto-Oncogênicas/metabolismo , Proteínas Proto-Oncogênicas c-raf/metabolismo , Proteínas Proto-Oncogênicas c-raf/farmacologia , Proteínas Repressoras , Fatores de Transcrição/metabolismoRESUMO
The generation of specific humoral and cellular immune responses plays a pivotal role in the development of effective vaccines against tumors. Especially the presence of antigen-specific, cytotoxic T cells influences the outcome of therapeutic cancer vaccinations. Different strategies, ranging from delivering antigen-encoding mRNAs to peptides or full antigens, are accessible but often suffer from insufficient immunogenicity and require immune-boosting adjuvants as well as carrier platforms to ensure stability and adequate retention. Here, we introduce a pH-responsive nanogel platform as a two-component antitumor vaccine that is safe for intravenous application and elicits robust immune responses in vitro and in vivo. The underlying chemical design allows for straightforward covalent attachment of a model antigen (ovalbumin) and an immune adjuvant (imidazoquinoline-type TLR7/8 agonist) onto the same nanocarrier system. In addition to eliciting antigen-specific T and B cell responses that outperform mixtures of individual components, our two-component nanovaccine leads in prophylactic and therapeutic studies to an antigen-specific growth reduction of different tumors expressing ovalbumin intracellularly or on their surface. Regarding the versatile opportunities for functionalization, our nanogels are promising for the development of highly customized and potent nanovaccines.
Assuntos
Vacinas Anticâncer , Neoplasias , Receptor 7 Toll-Like , Receptor 8 Toll-Like , Adjuvantes Imunológicos , Animais , Antígenos , Imunidade Celular , Camundongos , Camundongos Endogâmicos C57BL , Nanogéis , Neoplasias/terapia , Ovalbumina , Receptor 7 Toll-Like/agonistas , Receptor 8 Toll-Like/agonistasRESUMO
Tumors exhibit a variety of strategies to dampen antitumor immune responses. With an aim to identify factors that are secreted from tumor cells, we performed an unbiased mass spectrometry-based secretome analysis in lung cancer cells. Interleukin-6 (IL-6) has been identified as a prominent factor secreted by tumor cells and cancer-associated fibroblasts isolated from cancer patients. Incubation of dendritic cell (DC) cultures with tumor cell supernatants inhibited the production of IL-12p70 in DCs but not the surface expression of other activation markers which is reversed by treatment with IL-6 antibody. Defects in IL-12p70 production in the DCs inhibited the differentiation of Th1 but not Th2 and Th17 cells from naïve CD4+ T cells. We also demonstrate that the classical mitogen-activated protein kinase, ERK5/MAPK7, is required for IL-6 production in tumor cells. Inhibition of ERK5 activity or depletion of ERK5 prevented IL-6 production in tumor cells, which could be exploited for enhancing antitumor immune responses.
Assuntos
Terapia de Imunossupressão , Interleucina-6/metabolismo , Proteína Quinase 7 Ativada por Mitógeno/metabolismo , Neoplasias/imunologia , Diferenciação Celular/imunologia , Linhagem Celular Tumoral , Sobrevivência Celular , Células Dendríticas/metabolismo , Humanos , Interleucina-12/metabolismo , Proteína Quinase 7 Ativada por Mitógeno/antagonistas & inibidores , Modelos Biológicos , Monócitos/metabolismo , Neoplasias/patologia , RNA Interferente Pequeno/metabolismo , Células Th1/imunologiaRESUMO
CD22 [Siglec-2 (sialic acid-binding, immunoglobulin-like lectin-2)], a negative regulator of B-cell signalling, binds to alpha2,6- sialic acid-linked glycoconjugates, including a sialyl-Tn antigen that is one of the typical tumour-associated carbohydrate antigens expressed on various mucins. Many epithelial tumours secrete mucins into tissues and/or the bloodstream. Mouse mammary adenocarcinoma cells, TA3-Ha, produce a mucin named epiglycanin, but a subline of them, TA3-St, does not. Epiglycanin binds to CD22 and inhibits B-cell signalling in vitro. The in vivo effect of mucins in the tumour-bearing state was investigated using these cell lines. It should be noted that splenic MZ (marginal zone) B-cells were dramatically reduced in the mice bearing TA3-Ha cells but not in those bearing TA3-St cells, this being consistent with the finding that the thymus-independent response was reduced in these mice. When the mucins were administered to normal mice, a portion of them was detected in the splenic MZ associated with the MZ B-cells. Furthermore, administration of mucins to normal mice clearly reduced the splenic MZ B-cells, similar to tumour-bearing mice. These results indicate that mucins in the bloodstream interacted with CD22, which led to impairment of the splenic MZ B-cells in the tumour-bearing state.
Assuntos
Adenocarcinoma/metabolismo , Linfócitos B/imunologia , Mucinas/metabolismo , Lectina 2 Semelhante a Ig de Ligação ao Ácido Siálico/metabolismo , Baço/imunologia , Adenocarcinoma/imunologia , Animais , Antígenos T-Independentes/imunologia , Antígenos T-Independentes/metabolismo , Linfócitos B/metabolismo , Sítios de Ligação , Células CHO , Linhagem Celular Tumoral , Cricetinae , Cricetulus , Feminino , Glicoproteínas de Membrana/metabolismo , Camundongos , Camundongos Endogâmicos , Receptores de Antígenos de Linfócitos B/metabolismo , Lectina 2 Semelhante a Ig de Ligação ao Ácido Siálico/imunologia , Transdução de SinaisRESUMO
Rho GTPases control fundamental cellular processes and Cdc42 is a well-studied member of the family that controls filopodia formation and cell migration. Although the regulation of Cdc42 activity by nucleotide binding is well documented, the mechanisms driving its proteostasis are not clear. Here, we demonstrate that the highly conserved, RING domain containing E3 ubiquitin ligase XIAP controls the protein stability of Cdc42. XIAP binds to Cdc42 and directly conjugates poly ubiquitin chains to the Lysine 166 of Cdc42 targeting it for proteasomal degradation. Depletion of XIAP led to an increased protein stability and activity of Cdc42 in normal and tumor cells. Consistently, loss of XIAP enhances filopodia formation in a Cdc42-dependent manner and this phenomenon phenocopies EGF stimulation. Further, XIAP depletion promotes lung colonization of tumor cells in mice in a Cdc42-dependent manner. These observations shed molecular insights into ubiquitin-dependent regulation of Cdc42 and that of actin cytoskeleton.
Assuntos
Apoptose/genética , Neoplasias/genética , Proteínas Inibidoras de Apoptose Ligadas ao Cromossomo X/genética , Proteína cdc42 de Ligação ao GTP/genética , Citoesqueleto de Actina/genética , Animais , Movimento Celular/genética , Células HeLa , Humanos , Camundongos , Neoplasias/metabolismo , Neoplasias/patologia , Estabilidade Proteica , Pseudópodes/genética , Transdução de Sinais/genética , Ubiquitina/genética , Ubiquitina/metabolismo , Ubiquitina-Proteína Ligases/genética , Ubiquitinação/genética , Proteínas Inibidoras de Apoptose Ligadas ao Cromossomo X/metabolismo , Ensaios Antitumorais Modelo de Xenoenxerto , Proteína cdc42 de Ligação ao GTP/metabolismoRESUMO
Alterations in dendritic spine numbers are linked to deficits in learning and memory. While we previously revealed that postsynaptic plasticity-related gene 1 (PRG-1) controls lysophosphatidic acid (LPA) signaling at glutamatergic synapses via presynaptic LPA receptors, we now show that PRG-1 also affects spine density and synaptic plasticity in a cell-autonomous fashion via protein phosphatase 2A (PP2A)/ß1-integrin activation. PRG-1 deficiency reduces spine numbers and ß1-integrin activation, alters long-term potentiation (LTP), and impairs spatial memory. The intracellular PRG-1 C terminus interacts in an LPA-dependent fashion with PP2A, thus modulating its phosphatase activity at the postsynaptic density. This results in recruitment of adhesome components src, paxillin, and talin to lipid rafts and ultimately in activation of ß1-integrins. Consistent with these findings, activation of PP2A with FTY720 rescues defects in spine density and LTP of PRG-1-deficient animals. These results disclose a mechanism by which bioactive lipid signaling via PRG-1 could affect synaptic plasticity and memory formation.
Assuntos
Espinhas Dendríticas/metabolismo , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Integrina beta1/metabolismo , Lisofosfolipídeos/metabolismo , Plasticidade Neuronal/fisiologia , Proteína Fosfatase 2/metabolismo , Sinapses/fisiologia , Animais , Células Cultivadas , Espinhas Dendríticas/genética , Adesões Focais/fisiologia , Fatores de Troca do Nucleotídeo Guanina/genética , Hipocampo/citologia , Hipocampo/metabolismo , Integrina beta1/genética , Potenciação de Longa Duração , Microdomínios da Membrana/metabolismo , Camundongos , Camundongos Knockout , Proteína Fosfatase 2/genética , Fatores de Troca de Nucleotídeo Guanina Rho , Transdução de SinaisRESUMO
Prohibitin 1 (PHB1) and PHB2 are evolutionarily conserved, ubiquitously expressed, pleotropic proteins that control various fundamental cellular processes, including proliferation, migration, metabolism, and death. Studies have unveiled a crucial role for plasma membrane-associated PHBs in regulating tumor metastasis, viral entry, and immune cell activation. A study now identifies a role for PHB1 in the activation of mast cells and allergic reactions mediated by immunoglobulin E (IgE). PHB1 was primarily localized in mast cell granules; however, in response to stimulation with antigen, PHB1 translocated to plasma membrane lipid rafts to form a ternary complex with the high-affinity IgE receptor FcεRIγ and the nonreceptor tyrosine kinase Syk. Syk became activated, which led to the activation of downstream signaling that stimulated mast cell degranulation and the secretion of cytokines. PHB1 was phosphorylated by the Src family tyrosine kinase Lyn, and palmitoylation of PHB1 was required for its association with the plasma membrane. These observations unveil a previously uncharacterized facet of prohibitin biology and shed further light on the proximal events that drive the activation of FcεRI by IgE in mast cells during allergic reactions.