Research Articles
Autophagic degradation of CNS myelin maintains axon integrity
Niki Ktena1, Stefanos Ioannis Kaplanis1, Irina Kolotuev2, Alexandros Georgilis1, Emmanouela Kallergi3, Vasiliki Stavroulaki1, Vassiliki Nikoletopoulou3, Maria Savvaki1, and Domna Karagogeos1
(Macro)autophagy is a major lysosome-dependent degradation mechanism which engulfs, removes and recycles unwanted cytoplasmic material, including damaged organelles and toxic protein aggregates. Although a few studies implicate autophagy in CNS demyelinating pathologies, its role, particularly in mature oligodendrocytes and CNS myelin, remains poorly studied. Here, using both pharmacological and genetic inhibition of the autophagic machinery, we provide evidence that autophagy is an essential mechanism for oligodendrocyte maturation in vitro. Our study reveals that two core myelin proteins, namely proteolipid protein (PLP) and myelin basic protein (MBP) are incorporated into autophagosomes in oligodendrocytes, resulting in their degradation. Furthermore, we ablated atg5, a core gene of the autophagic machinery, specifically in myelinating (...)
COX4-1 promotes mitochondrial supercomplex assembly and limits reactive oxide species production in radioresistant GBM
Claudia R. Oliva1, Md Yousuf Ali1,2, Susanne Flor1 and Corinne E. Griguer1
Glioblastoma (GBM) is a fatal disease with recurrences often associated with radioresistance. Although often effective at treating newly diagnosed GBM, increasing evidence suggests that radiotherapy-induced alterations in tumor metabolism promote GBM recurrence and aggressiveness. Using isogenic radiosensitive and radioresistant GBM cell lines and patient-derived xenolines, we found that acquired radioresistance is associated with a shift from a glycolytic metabolism to a more oxidative metabolism marked by a substantial increase in the activity of the mitochondrial respiratory chain complex cytochrome c oxidase (CcO). This elevated CcO activity was associated with a switch in the isoform expression of the CcO regulatory subunit COX4, from COX4-2 to COX4-1, assembly of CcO-containing mitochondrial supercomplexes (SCs), and reduced superoxide (O2●-) production. Overexpression of COX4-1 in the radiosensitive cells was sufficient to promote the switch from glycolytic to (...)
Evaluation of I-TAC as a potential early plasma marker to differentiate between critical and non-critical COVID-19
Yushan Zhang1, Chao Xu2, Nelson I. Agudelo Higuita3, Resham Bhattacharya4,5, Jennifer Holter Chakrabarty3 and Priyabrata Mukherjee1,5
INTRODUCTION The coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is not a single entity but a disease with an extraordinary spectrum of phenotypes.
p38 regulates the tumor suppressor PDCD4 via the TSC-mTORC1 pathway
Clarissa Braun1,2, Karl Katholnig1, Christopher Kaltenecker3, Monika Linke1, Nyamdelger Sukhbaatar1, Markus Hengstschläger1 and Thomas Weichhart1
Programmed cell death protein 4 (PDCD4) exerts critical functions as tumor suppressor and in immune cells to regulate inflammatory processes. The phosphoinositide 3-kinase (PI3K) promotes degradation of PDCD4 via mammalian target of rapamycin complex 1 (mTORC1). However, additional pathways that may regulate PDCD4 expression are largely ill-defined. In this study, we have found that activation of the mitogen-activated protein kinase p38 promoted degradation of PDCD4 in macrophages and fibroblasts. Mechanistically, we identified a pathway from p38 and its substrate MAP kinase-activated protein kinase 2 (MK2) to the tuberous sclerosis complex (TSC) to regulate mTORC1-dependent (...)
Targeting the TGFβ pathway in uterine carcinosarcoma
Shailendra Kumar Dhar Dwivedi1, Geeta Rao2, Anindya Dey1, Megan Buechel1, Yushan Zhang2, Min Zhang3, Da Yang3, Priyabrata Mukherjee2, Resham Bhattacharya1,4
Uterine carcinosarcoma (UCS) is a relatively infrequent, but extremely aggressive endometrial malignancy. Although surgery and chemotherapy have improved outcomes, overall survival (OS) remains dismal due to the lack of targeted therapy and biphasic (epithelial and mesenchymal) nature that renders the tumor aggressive and difficult to manage. Here we report a role of transforming growth factor-β (TGFβ) in maintaining epithelial to mesenchymal transition (EMT) phenotype and aggressiveness in UCS. Using a 3D-culture system, we evaluated the efficacy of the transforming growth factor-β receptor-I (TGFβR1) kinase inhibitor Galunisertib (GLT), alone and in combination with standard chemotherapeutic drugs used for the management of UCS. We demonstrate that GLT by inhibiting canonical and non-canonical signaling emanating from transforming growth factor-β1 (TGFβ1) reduces cellular viability, invasion, clonal growth and differentiation. (...)
HIF1α-dependent mitophagy facilitates cardiomyoblast differentiation
Jin-Feng Zhao1,#, Catherine E. Rodger1,#, George F. G. Allen1, Simone Weidlich1 and Ian G. Ganley1
Mitophagy is thought to play a key role in eliminating damaged mitochondria, with diseases such as cancer and neurodegeneration exhibiting defects in this process. Mitophagy is also involved in cell differentiation and maturation, potentially through modulating mitochondrial metabolic reprogramming. Here we examined mitophagy that is induced upon iron chelation and found that the transcriptional activity of HIF1α, in part through upregulation of BNIP3 and NIX, is an essential mediator of this pathway in SH-SY5Y cells. In contrast, HIF1α is dispensable for mitophagy occurring upon mitochondrial depolarisation. To examine the role of this pathway in a metabolic reprogramming and differentiation context, we utilised the H9c2 cell line model of cardiomyocyte maturation. During differentiation of these cardiomyoblasts, mitophagy increased and required HIF1α-dependent upregulation of NIX. Though HIF1α was essential for expression of key (...)
RPA and Pif1 cooperate to remove G-rich structures at both leading and lagging strand
Laetitia Maestroni1, Julien Audry1, Pierre Luciano1, Stéphane Coulon1, Vincent Géli1 and Yves Corda1
In Saccharomyces cerevisiae, the absence of Pif1 helicase induces the instability of G4-containing CEB1 minisatellite during leading strand but not lagging strand replication. We report that RPA and Pif1 cooperate to maintain CEB1 stability when the G4 forming strand is either on the leading or lagging strand templates. At the leading strand, RPA acts in the same pathway as Pif1 to maintain CEB1 stability. Consistent with this result, RPA co-precipitates with Pif1. This association between Pif1 and RPA is affected by the rfa1-D228Y mutation that lowers the affinity of RPA in particular for G-rich single-stranded DNA. At the lagging strand, in contrast to pif1∆, the rfa1-D228Y mutation strongly increases the frequency of CEB1 rearrangements. We explain that Pif1 is dispensable at the lagging strand DNA by the ability of RPA by itself to prevent formation of stable G-rich secondary structures during lagging (…)
LTX-315 sequentially promotes lymphocyte-independent and lymphocyte-dependent antitumor effects
Hsin-Wei Liao1,#, Christopher Garris1,#, Christina Pfirschke1, Steffen Rickelt2, Sean Arlauckas1, Marie Siwicki1, Rainer H. Kohler1, Ralph Weissleder1, Vibeke Sundvold-Gjerstad3, Baldur Sveinbjørnsson3,4, Øystein Rekdal3,4 and Mikael J. Pittet1
LTX-315 is an oncolytic peptide that has antitumor efficacy in mice grafted with various tumor cell lines and is currently being tested in phase II clinical trials. Here we aimed to further evaluate LTX-315 in conditional genetic mouse models of cancer that typically resist current treatment options and to better understand the drug’s mode of action in vivo. We report LTX-315 mediates profound antitumor effects against Braf- and Pten-driven melanoma and delays the progression of Kras- and P53-driven soft tissue sarcoma in mice. Additionally, we show in melanoma that LTX-315 triggers two sequential phases of antitumor response. The first phase of response, which begins within minutes of drug delivery into tumors, is defined by disrupted tumor vasculature and decreased tumor burden and occurs independently of (...)
Gold Nanoparticles sensitize pancreatic cancer cells to gemcitabine
Yanyan Huai1, Yushan Zhang1, Xunhao Xiong1, Shamik Das2, Resham Bhattacharya2 and Priyabrata Mukherjee1,2
INTRODUCTION Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal disease. The mortality rate closely parallels that of incidence [1][2]. The current standard of care for advanced stage PDAC patients includes