1,082 research outputs found
DYNAMIC REGULATION OF MITOCHONDRIAL STAT3 AND ITS ASSOCIATION WITH CYPD
In recent years, a number of nuclear transcription factors have been shown to be present in the mitochondria where they have distinct roles in regulating mitochondrial function. Signal Transducer and Activator of Transcription 3 (STAT3), classically activated by the JAK family of receptor associated tyrosine kinases to drive nuclear gene expression, is one such transcription factor with a unique mitochondrial role. There, it has been shown to support oxidative phosphorylation, regulate mitochondrial-encoded transcripts, and be key for the transformation and growth of a number of different cancers. Despite its well-characterized functional importance at the level of the mitochondria, the mechanism through which mitochondrial STAT3 acts and how it is regulated has not been as well studied.
Using various cell culture models, we now show that mitochondrial STAT3 is dynamically regulated by oxidative stress and cytokine treatment in the acute setting. Under these conditions we have observed a rapid loss of mitochondrial STAT3 that recovers to baseline conditions with time. During this recovery phase we have noted that mitochondrial STAT3 becomes competent to bind to Cyclophilin D (CypD), the key regulator and activator of the mitochondrial permeability transition pore (MPTP). This is particularly the case with oxidative insults, which we believe may represent an important homeostatic mechanism for the cell. Intriguingly, chronic stimulation with certain stressors seems to increase mitochondrial STAT3 levels suggesting differential regulation in the acute versus chronic setting.
The regulation of mitochondrial STAT3 levels by various stimuli points to a novel signaling pathway potentially linking mitochondrial responses with those of the cell. Unification of responses throughout the cell would seem to serve a clear adaptive advantage, particularly in coupling nuclear regulation with metabolic demands as dictated by the mitochondria. Extramitochondrial signaling, also known as the mitochondrial retrograde response, has emerged as an important homeostatic mechanism in lower organisms, but its signaling components have not been well characterized at the mammalian level. Our results point to a role for mitochondrial STAT3 in sensing cellular inputs, whereby its regulation and subsequent association with CypD may have implications in overall mitochondrial quality control. Though the inner workings of this signaling cascade are just beginning to be elucidated, they suggest the existence of a previously unappreciated pathway at the mitochondrial level
The Emerging Role of CAR T Cell Therapy in Relapsed/Refractory Hodgkin Lymphoma
Treatment for Hodgkin lymphoma (HL) has evolved considerably from the time it was originally described in the 19th century with many patients now being cured with frontline therapy. Despite these advances, upwards of 10% of patients experience progressive disease after initial therapy with an even higher percentage relapsing. Until recently there had been limited therapeutic options for relapsed and/or refractory HL outside of highly intensive chemotherapy with stem cell rescue. Improved understanding of the pathophysiology of HL, coupled with the emergence of more targeted therapeutics, has reshaped how we view the treatment of relapsed/refractory HL and its prognosis. With this, there has been an increased focus on immunotherapies that can reprogram the immune system to better overcome the immunosuppressive milieu found in HL for improved cancer cell killing. In particular, chimeric antigen receptor (CAR) T cells are emerging as a valuable therapeutic tool in this area. Building on the success of antibody-drug conjugates directed against CD30, CAR T cells engineered to recognize the same antigen are now reaching patients. Though still in its infancy, CAR T therapy for relapsed/refractory HL has shown exceptional promise in early-stage clinical trials with the potential for durable responses even in patients who had progressed through multiple lines of prior therapy. Here we will review currently available data on the use of CAR T cells in HL, strategies to optimize their effectiveness, and how this therapy may fit into the treatment paradigm of HL going forward
Crosslinking Studies of Protein-Protein Interactions in Nonribosomal Peptide Biosynthesis
SummarySelective protein-protein interactions between nonribosomal peptide synthetase (NRPS) proteins, governed by communication-mediating (COM) domains, are responsible for proper translocation of biosynthetic intermediates to produce the natural product. In this study, we developed a crosslinking assay, utilizing bioorthogonal probes compatible with carrier protein modification, for probing the protein interactions between COM domains of NRPS enzymes. Employing the Huisgen 1,3-dipolar cycloaddition of azides and alkynes, we examined crosslinking of cognate NRPS modules within the tyrocidine pathway and demonstrated the sensitivity of our panel of crosslinking probes toward the selective protein interactions of compatible COM domains. These studies indicate that copper-free crosslinking substrates uniquely offer a diagnostic probe for protein-protein interactions. Likewise, these crosslinking probes serve as ideal chemical tools for structural studies between NRPS modules where functional assays are lacking
Stem Cell Transplantation As A Dynamical System: Are Clinical Outcomes Deterministic?
Outcomes in stem cell transplantation (SCT) are modeled using probability
theory. However the clinical course following SCT appears to demonstrate many
characteristics of dynamical systems, especially when outcomes are considered
in the context of immune reconstitution. Dynamical systems tend to evolve over
time according to mathematically determined rules. Characteristically, the
future states of the system are predicated on the states preceding them, and
there is sensitivity to initial conditions. In SCT, the interaction between
donor T cells and the recipient may be considered as such a system in which,
graft source, conditioning and early immunosuppression profoundly influence
immune reconstitution over time. This eventually determines clinical outcomes,
either the emergence of tolerance or the development of graft versus host
disease. In this paper parallels between SCT and dynamical systems are explored
and a conceptual framework for developing mathematical models to understand
disparate transplant outcomes is proposed.Comment: 23 pages, 4 figures. Updated version with additional data, 2 new
figures and editorial revisions. New authors adde
Determining the Quantitative Principles of T Cell Response to Antigenic Disparity in Stem Cell Transplantation
Alloreactivity compromising clinical outcomes in stem cell transplantation is observed despite HLA matching of donors and recipients. This has its origin in the variation between the exomes of the two, which provides the basis for minor histocompatibility antigens (mHA). The mHA presented on the HLA class I and II molecules and the ensuing T cell response to these antigens results in graft vs. host disease. In this paper, results of a whole exome sequencing study are presented, with resulting alloreactive polymorphic peptides and their HLA class I and HLA class II (DRB1) binding affinity quantified. Large libraries of potentially alloreactive recipient peptides binding both sets of molecules were identified, with HLA-DRB1 generally presenting a greater number of peptides. These results are used to develop a quantitative framework to understand the immunobiology of transplantation. A tensor-based approach is used to derive the equations needed to determine the alloreactive donor T cell response from the mHA-HLA binding affinity and protein expression data. This approach may be used in future studies to simulate the magnitude of expected donor T cell response and determine the risk for alloreactive complications in HLA matched or mismatched hematopoietic cell and solid organ transplantation
Quantum computing with antiferromagnetic spin clusters
We show that a wide range of spin clusters with antiferromagnetic
intracluster exchange interaction allows one to define a qubit. For these spin
cluster qubits, initialization, quantum gate operation, and readout are
possible using the same techniques as for single spins. Quantum gate operation
for the spin cluster qubit does not require control over the intracluster
exchange interaction. Electric and magnetic fields necessary to effect quantum
gates need only be controlled on the length scale of the spin cluster rather
than the scale for a single spin. Here, we calculate the energy gap separating
the logical qubit states from the next excited state and the matrix elements
which determine quantum gate operation times. We discuss spin cluster qubits
formed by one- and two-dimensional arrays of s=1/2 spins as well as clusters
formed by spins s>1/2. We illustrate the advantages of spin cluster qubits for
various suggested implementations of spin qubits and analyze the scaling of
decoherence time with spin cluster size.Comment: 15 pages, 7 figures; minor change
Tiny Sc allows the chains to rattle: Impact of Lu and Y doping on the charge density wave in ScVSn
The kagome metals display an intriguing variety of electronic and magnetic
phases arising from the connectivity of atoms on a kagome lattice. A growing
number of these materials with vanadium kagome nets host charge density waves
(CDWs) at low temperatures including ScVSn, CsVSb, and
VSb. Curiously, only the Sc version of the VSn
HfFeGe-type materials hosts a CDW (Gd-Lu, Y, Sc). In this study
we investigate the role of rare earth size in CDW formation in the
VSn compounds. Magnetization measurements on our single crystals of
(Sc,Lu)VSn and (Sc,Y)VSn establish that the CDW is suppressed
by substitution of Sc by larger Lu or Y. Single crystal x-ray diffraction
reveals that compressible Sn-Sn bonds accommodate the larger rare earth atoms
within loosely packed -Sn-Sn chains without significantly expanding the
lattice. We propose that Sc provides the extra room in these chains crucial to
CDW formation in ScVSn. Our rattling chain model explains why both
physical pressure and substitution by larger rare earths hinder CDW formation
despite opposite impacts on lattice size. We emphasize the cooperative effect
of pressure and rare earth size by demonstrating that pressure further
suppresses the CDW in a Lu-doped ScVSn crystal. Our model not only
addresses why a CDW only forms in the VSn materials with tiny Sc, it
also advances to our understanding of why unusual CDWs form in the kagome
metals.Comment: 28 pages, 9 figures, crystallographic information files for LuV6Sn6
and YV6Sn6 along with supplemental materials in ancillary file
SMA CO(J=6-5) and 435 micron interferometric imaging of the nuclear region of Arp 220
We have used the Submillimeter Array (SMA) to make the first interferometric
observations (beam size ~1") of the 12CO J=6-5 line and 435 micron (690 GHz)
continuum emission toward the central region of the nearby ULIRG Arp 220. These
observations resolve the eastern and western nuclei from each other, in both
the molecular line and dust continuum emission. At 435 micron, the peak
intensity of the western nucleus is stronger than the eastern nucleus, and the
difference in peak intensities is less than at longer wavelengths. Fitting a
simple model to the dust emission observed between 1.3 mm and 435 micron
suggests that dust emissivity power law index in the western nucleus is near
unity and steeper in the eastern nucleus, about 2, and that the dust emission
is optically thick at the shorter wavelength. Comparison with single dish
measurements indicate that the interferometer observations are missing ~60% of
the dust emission, most likely from a spatially extended component to which
these observations are not sensitive. The 12CO J=6-5 line observations clearly
resolve kinematically the two nuclei. The distribution and kinematics of the
12CO J=6-5 line appear to be very similar to lower J CO lies observed at
similar resolution. Analysis of multiple 12CO line intensities indicates that
the molecular gas in both nuclei have similar excitation conditions, although
the western nucleus is warmer and denser. The excitation conditions are similar
to those found in other extreme environments, including M82, Mrk 231, and BR
1202-0725. Simultaneous lower resolution observations of the 12CO, 13CO, and
C18O J=2-1 lines show that the 13CO and C18O lines have similar intensities,
which suggests that both of these lines are optically thick, or possibly that
extreme high mass star formation has produced in an overabundance of C18O.Comment: 13 pages (emulateapj), 10 figures, Accepted for publication in Ap
Discovery and characterization of small molecules that target the Ral GTPase
The Ras-like GTPases RalA and B are important drivers of tumor growth and metastasis. Chemicals that block Ral function would be valuable as research tools and for cancer therapeutics. Here, we used protein structure analysis and virtual screening to identify drug-like molecules that bind a site on the GDP-form of Ral. Compounds RBC6, RBC8 and RBC10 inhibited Ral binding to its effector RalBP1, Ral-mediated cell spreading in murine fibroblasts and anchorage-independent growth of human cancer cell lines. Binding of RBC8 derivative BQU57 to RalB was confirmed by isothermal titration calorimetry, surface plasma resonance and 15N-HSQC NMR. RBC8 and BQU57 show selectivity for Ral relative to Ras or Rho and inhibit xenograft tumor growth similar to depletion of Ral by siRNA. Our results show the utility of structure-based discovery for development of therapeutics for Ral-dependent cancers
Stress-induced dynamic regulation of mitochondrial STAT3 and its association with cyclophilin D reduces mitochondrial ROS production
Signal Transducer and Activator of Transcription 3 (STAT3) has been tied to various physiological and pathological functions, mainly as a transcription factor that translocates to the nucleus upon tyrosine phosphorylation induced by cytokine stimulation. In addition, a small pool of STAT3 resides in the mitochondria where it serves as a sensor for various metabolic stressors including reactive oxygen species (ROS). Mitochondrially-localized STAT3 largely exerts its effects through direct or indirect regulation of the activity of the electron transport chain (ETC). It has been assumed that STAT3 amounts in the mitochondria are static. We showed that various stimuli, including oxidative stress and cytokines, triggered a signaling cascade that resulted in a rapid loss of mitochondrially-localized STAT3. Recovery of the mitochondrial pool of STAT3 over time depended upon phosphorylation of Ser727 in STAT3 and new protein synthesis. Under these conditions, mitochondrially-localized STAT3 also became competent to bind to cyclophilin D (CypD). Binding of STAT3 to CypD was mediated by the N-terminus of STAT3, which was also important for reducing mitochondrial ROS production after oxidative stress. These results outline a role for mitochondrially-localized STAT3 in sensing and responding to external stimuli
- …