Regulation of death receptor signaling by the autophagy protein TP53INP2

TP53INP2 positively regulates autophagy by binding to Atg8 proteins. Here, we uncover a novel role of TP53INP2 in death-receptor signaling. TP53INP2 sensitizes cells to apoptosis induced by death receptor ligands. In keeping with this, TP53INP2 deficiency in cultured cells or mouse livers protects against death receptor-induced apoptosis. TP53INP2 binds caspase-8 and the ubiquitin ligase TRAF6, thereby promoting the ubiquitination and activation of caspase-8 by TRAF6. We have defined a TRAF6-interacting motif (TIM) and a ubiquitin-interacting motif in TP53INP2, enabling it to function as a scaffold bridging already ubiquitinated caspase-8 to TRAF6 for further polyubiquitination of caspase-8. Mutations of key TIM residues in TP53INP2 abrogate its interaction with TRAF6 and caspase-8, and subsequently reduce levels of death receptor-induced apoptosis. A screen of cancer cell lines showed that those with higher protein levels of TP53INP2 are more prone to TRAIL-induced apoptosis, making TP53INP2 a potential predictive marker of cancer cell responsiveness to TRAIL treatment. These findings uncover a novel mechanism for the regulation of caspase-8 ubiquitination and reveal TP53INP2 as an important regulator of the death receptor pathway

Regulation of death receptor signaling by the autophagy protein TP53INP2

TP53INP2 positively regulates autophagy by binding to Atg8 proteins. Here, we uncover a novel role of TP53INP2 in death‐receptor signaling. TP53INP2 sensitizes cells to apoptosis induced by death receptor ligands. In keeping with this, TP53INP2 deficiency in cultured cells or mouse livers protects against death receptor‐induced apoptosis. TP53INP2 binds caspase‐8 and the ubiquitin ligase TRAF6, thereby promoting the ubiquitination and activation of caspase‐8 by TRAF6. We have defined a TRAF6‐interacting motif (TIM) and a ubiquitin‐interacting motif in TP53INP2, enabling it to function as a scaffold bridging already ubiquitinated caspase‐8 to TRAF6 for further polyubiquitination of caspase‐8. Mutations of key TIM residues in TP53INP2 abrogate its interaction with TRAF6 and caspase‐8, and subsequently reduce levels of death receptor‐induced apoptosis. A screen of cancer cell lines showed that those with higher protein levels of TP53INP2 are more prone to TRAIL‐induced apoptosis, making TP53INP2 a potential predictive marker of cancer cell responsiveness to TRAIL treatment. These findings uncover a novel mechanism for the regulation of caspase‐8 ubiquitination and reveal TP53INP2 as an important regulator of the death receptor pathway

Phospholipids Trigger Cryptococcus neoformans Capsular Enlargement during Interactions with Amoebae and Macrophages

A remarkable aspect of the interaction of Cryptococcus neoformans with mammalian hosts is a consistent increase in capsule volume. Given that many aspects of the interaction of C. neoformans with macrophages are also observed with amoebae, we hypothesized that the capsule enlargement phenomenon also had a protozoan parallel. Incubation of C. neoformans with Acanthamoeba castellanii resulted in C. neoformans capsular enlargement. The phenomenon required contact between fungal and protozoan cells but did not require amoeba viability. Analysis of amoebae extracts showed that the likely stimuli for capsule enlargement were protozoan polar lipids. Extracts from macrophages and mammalian serum also triggered cryptococcal capsular enlargement. C. neoformans capsule enlargement required expression of fungal phospholipase B, but not phospholipase C. Purified phospholipids, in particular, phosphatidylcholine, and derived molecules triggered capsular enlargement with the subsequent formation of giant cells. These results implicate phospholipids as a trigger for both C. neoformans capsule enlargement in vivo and exopolysaccharide production. The observation that the incubation of C. neoformans with phospholipids led to the formation of giant cells provides the means to generate these enigmatic cells in vitro. Protozoan- or mammalian-derived polar lipids could represent a danger signal for C. neoformans that triggers capsular enlargement as a non-specific defense mechanism against potential predatory cells. Hence, phospholipids are the first host-derived molecules identified to trigger capsular enlargement. The parallels apparent in the capsular response of C. neoformans to both amoebae and macrophages provide additional support for the notion that certain aspects of cryptococcal virulence emerged as a consequence of environmental interactions with other microorganisms such as protists

Effects of immunosuppressive drugs on COVID-19 severity in patients with autoimmune hepatitis

Background: We investigated associations between baseline use of immunosuppressive drugs and severity of Coronavirus Disease 2019 (COVID-19) in autoimmune hepatitis (AIH). Patients and methods: Data of AIH patients with laboratory confirmed COVID-19 were retrospectively collected from 15 countries. The outcomes of AIH patients who were on immunosuppression at the time of COVID-19 were compared to patients who were not on AIH medication. The clinical courses of COVID-19 were classified as (i)-no hospitalization, (ii)-hospitalization without oxygen supplementation, (iii)-hospitalization with oxygen supplementation by nasal cannula or mask, (iv)-intensive care unit (ICU) admission with non-invasive mechanical ventilation, (v)-ICU admission with invasive mechanical ventilation or (vi)-death and analysed using ordinal logistic regression. Results: We included 254 AIH patients (79.5%, female) with a median age of 50 (range, 17-85) years. At the onset of COVID-19, 234 patients (92.1%) were on treatment with glucocorticoids (n = 156), thiopurines (n = 151), mycophenolate mofetil (n = 22) or tacrolimus (n = 16), alone or in combinations. Overall, 94 (37%) patients were hospitalized and 18 (7.1%) patients died. Use of systemic glucocorticoids (adjusted odds ratio [aOR] 4.73, 95% CI 1.12-25.89) and thiopurines (aOR 4.78, 95% CI 1.33-23.50) for AIH was associated with worse COVID-19 severity, after adjusting for age-sex, comorbidities and presence of cirrhosis. Baseline treatment with mycophenolate mofetil (aOR 3.56, 95% CI 0.76-20.56) and tacrolimus (aOR 4.09, 95% CI 0.69-27.00) were also associated with more severe COVID-19 courses in a smaller subset of treated patients. Conclusion: Baseline treatment with systemic glucocorticoids or thiopurines prior to the onset of COVID-19 was significantly associated with COVID-19 severity in patients with AIH.Fil: Efe, Cumali. Harran University Hospita; TurquíaFil: Lammert, Craig. University School of Medicine Indianapolis; Estados UnidosFil: Taşçılar, Koray. Universitat Erlangen-Nuremberg; AlemaniaFil: Dhanasekaran, Renumathy. University of Stanford; Estados UnidosFil: Ebik, Berat. Gazi Yasargil Education And Research Hospital; TurquíaFil: Higuera de la Tijera, Fatima. Hospital General de México; MéxicoFil: Calışkan, Ali R.. No especifíca;Fil: Peralta, Mirta. Gobierno de la Ciudad de Buenos Aires. Hospital de Infecciosas "Dr. Francisco Javier Muñiz"; ArgentinaFil: Gerussi, Alessio. Università degli Studi di Milano; ItaliaFil: Massoumi, Hatef. No especifíca;Fil: Catana, Andreea M.. Harvard Medical School; Estados UnidosFil: Purnak, Tugrul. University of Texas; Estados UnidosFil: Rigamonti, Cristina. Università del Piemonte Orientale ; ItaliaFil: Aldana, Andres J. G.. Fundacion Santa Fe de Bogota; ColombiaFil: Khakoo, Nidah. Miami University; Estados UnidosFil: Nazal, Leyla. Clinica Las Condes; ChileFil: Frager, Shalom. Montefiore Medical Center; Estados UnidosFil: Demir, Nurhan. Haseki Training And Research Hospital; TurquíaFil: Irak, Kader. Kanuni Sultan Suleyman Training And Research Hospital; TurquíaFil: Melekoğlu Ellik, Zeynep. Ankara University Medical Faculty; TurquíaFil: Kacmaz, Hüseyin. Adıyaman University; TurquíaFil: Balaban, Yasemin. Hacettepe University; TurquíaFil: Atay, Kadri. No especifíca;Fil: Eren, Fatih. No especifíca;Fil: Alvares da-Silva, Mario R.. Universidade Federal do Rio Grande do Sul; BrasilFil: Cristoferi, Laura. Università degli Studi di Milano; ItaliaFil: Urzua, Álvaro. Universidad de Chile; ChileFil: Eşkazan, Tuğçe. Cerrahpaşa School of Medicine; TurquíaFil: Magro, Bianca. No especifíca;Fil: Snijders, Romee. No especifíca;Fil: Barutçu, Sezgin. No especifíca;Fil: Lytvyak, Ellina. University of Alberta; CanadáFil: Zazueta, Godolfino M.. Instituto Nacional de la Nutrición Salvador Zubiran; MéxicoFil: Demirezer Bolat, Aylin. Ankara City Hospital; TurquíaFil: Aydın, Mesut. Van Yuzuncu Yil University; TurquíaFil: Amorós Martín, Alexandra Noemí. No especifíca;Fil: De Martin, Eleonora. No especifíca;Fil: Ekin, Nazım. No especifíca;Fil: Yıldırım, Sümeyra. No especifíca;Fil: Yavuz, Ahmet. No especifíca;Fil: Bıyık, Murat. Necmettin Erbakan University; TurquíaFil: Narro, Graciela C.. Instituto Nacional de la Nutrición Salvador Zubiran; MéxicoFil: Bıyık, Murat. Uludag University; TurquíaFil: Kıyıcı, Murat. No especifíca;Fil: Kahramanoğlu Aksoy, Evrim. No especifíca;Fil: Vincent, Maria. No especifíca;Fil: Carr, Rotonya M.. University of Pennsylvania; Estados UnidosFil: Günşar, Fulya. No especifíca;Fil: Reyes, Eira C.. Hepatology Unit. Hospital Militar Central de México; MéxicoFil: Harputluoğlu, Murat. Inönü University School of Medicine; TurquíaFil: Aloman, Costica. Rush University Medical Center; Estados UnidosFil: Gatselis, Nikolaos K.. University Hospital Of Larissa; GreciaFil: Üstündağ, Yücel. No especifíca;Fil: Brahm, Javier. Clinica Las Condes; ChileFil: Vargas, Nataly C. E.. Hospital Nacional Almanzor Aguinaga Asenjo; PerúFil: Güzelbulut, Fatih. No especifíca;Fil: Garcia, Sandro R.. Hospital Iv Víctor Lazarte Echegaray; PerúFil: Aguirre, Jonathan. Hospital Angeles del Pedregal; MéxicoFil: Anders, Margarita. Hospital Alemán; ArgentinaFil: Ratusnu, Natalia. Hospital Regional de Ushuaia; ArgentinaFil: Hatemi, Ibrahim. No especifíca;Fil: Mendizabal, Manuel. Universidad Austral; ArgentinaFil: Floreani, Annarosa. Università di Padova; ItaliaFil: Fagiuoli, Stefano. No especifíca;Fil: Silva, Marcelo. Universidad Austral; ArgentinaFil: Idilman, Ramazan. No especifíca;Fil: Satapathy, Sanjaya K.. No especifíca;Fil: Silveira, Marina. University of Yale. School of Medicine; Estados UnidosFil: Drenth, Joost P. H.. No especifíca;Fil: Dalekos, George N.. No especifíca;Fil: N.Assis, David. University of Yale. School of Medicine; Estados UnidosFil: Björnsson, Einar. No especifíca;Fil: Boyer, James L.. University of Yale. School of Medicine; Estados UnidosFil: Yoshida, Eric M.. University of British Columbia; CanadáFil: Invernizzi, Pietro. Università degli Studi di Milano; ItaliaFil: Levy, Cynthia. University of Miami; Estados UnidosFil: Montano Loza, Aldo J.. University of Alberta; CanadáFil: Schiano, Thomas D.. No especifíca;Fil: Ridruejo, Ezequiel. Universidad Austral; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. CEMIC-CONICET. Centro de Educaciones Médicas e Investigaciones Clínicas "Norberto Quirno". CEMIC-CONICET; ArgentinaFil: Wahlin, Staffan. No especifíca