Cell biology
Abstract
Emerging knowledge indicates the difficulty in categorizing unusual cystic fibrosis (CF) mutations, with regard to both pathogenic mechanism and theratype. As case in point, we present data concerning P67L mutation of the cystic fibrosis transmembrane conductance regulator (CFTR), a defect carried by a small number of individuals with CF and sometimes attributed to a channel conductance abnormality. Findings from our laboratory and others establish that P67L causes protein misfolding, disrupts maturation, confers gating defects, is thermally stable, and exhibits near normal conductance. These results provide one framework by which rare CF alleles such as P67L can be more comprehensively profiled vis-à-vis molecular pathogenesis. We also demonstrate that emerging CF treatments — ivacaftor and lumacaftor — can mediate pronounced pharmacologic activation of P67L CFTR. Infrequent CF alleles are often improperly characterized, in part, due to the small numbers of patients involved. Moreover, access to new personalized treatments among patients with ultra-orphan genotypes has been limited by difficulty arranging phase III clinical trials, and off-label prescribing has been impaired by high drug cost and difficulty arranging third party reimbursement. Rare CFTR mutations such as P67L are emblematic of the challenges to “precision” medicine, including use of the best available mechanistic knowledge to treat patients with unusual forms of disease.
Authors
Carleen M. Sabusap, Wei Wang, Carmel M. McNicholas, W. Joon Chung, Lianwu Fu, Hui Wen, Marina Mazur, Kevin L. Kirk, James F. Collawn, Jeong S. Hong, Eric J. Sorscher
Abstract
Kidney fibrosis following kidney injury is an unresolved health problem and causes significant morbidity and mortality worldwide. In a study into its molecular mechanism, we identified essential causative features. Acute or chronic kidney injury causes sustained elevation of a disintegrin and metalloprotease 17 (ADAM17); of its cleavage-activated proligand substrates, in particular of pro-TNFα and the EGFR ligand amphiregulin (pro-AREG); and of the substrates’ receptors. As a consequence, EGFR is persistently activated and triggers the synthesis and release of proinflammatory and profibrotic factors, resulting in macrophage/neutrophil ingress and fibrosis. ADAM17 hypomorphic mice, specific ADAM17 inhibitor–treated WT mice, or mice with inducible KO of ADAM17 in proximal tubule (Slc34a1-Cre) were significantly protected against these effects. In vitro, in proximal tubule cells, we show that AREG has unique profibrotic actions that are potentiated by TNFα-induced AREG cleavage. In vivo, in acute kidney injury (AKI) and chronic kidney disease (CKD, fibrosis) patients, soluble AREG is indeed highly upregulated in human urine, and both ADAM17 and AREG expression show strong positive correlation with fibrosis markers in related kidney biopsies. Our results indicate that targeting of the ADAM17 pathway represents a therapeutic target for human kidney fibrosis.
Authors
Eirini Kefaloyianni, Muthu Lakshmi Muthu, Jakob Kaeppler, Xiaoming Sun, Venkata Sabbisetti, Athena Chalaris, Stefan Rose-John, Eitan Wong, Irit Sagi, Sushrut S. Waikar, Helmut Rennke, Benjamin D. Humphreys, Joseph V. Bonventre, Andreas Herrlich
Abstract
Motile airway cilia that propel contaminants out of the lung are oriented in a common direction by planar cell polarity (PCP) signaling, which localizes PCP protein complexes to opposite cell sides throughout the epithelium to orient cytoskeletal remodeling. In airway epithelia, PCP is determined in a 2-phase process. First, cell-cell communication via PCP complexes polarizes all cells with respect to the proximal-distal tissue axis. Second, during ciliogenesis, multiciliated cells (MCCs) undergo cytoskeletal remodeling to orient their cilia in the proximal direction. The second phase not only directs cilium polarization, but also consolidates polarization across the epithelium. Here, we demonstrate that in airway epithelia, PCP depends on MCC differentiation. PCP mutant epithelia have misaligned cilia, and also display defective barrier function and regeneration, indicating that PCP regulates multiple aspects of airway epithelial homeostasis. In humans, MCCs are often sparse in chronic inflammatory diseases, and these airways exhibit PCP dysfunction. The presence of insufficient MCCs impairs mucociliary clearance in part by disrupting PCP-driven polarization of the epithelium. Consistent with defective PCP, barrier function and regeneration are also disrupted. Pharmacological stimulation of MCC differentiation restores PCP and reverses these defects, suggesting its potential for broad therapeutic benefit in chronic inflammatory disease.
Authors
Eszter K. Vladar, Jayakar V. Nayak, Carlos E. Milla, Jeffrey D. Axelrod
Abstract
Senescent cells accumulate in many tissues as animals age and are considered to underlie several aging-associated pathologies. The tumor suppressors p19ARF and p16INK4a, both of which are encoded in the
Authors
Michihiro Hashimoto, Azusa Asai, Hiroyuki Kawagishi, Ryuta Mikawa, Yuji Iwashita, Kazuki Kanayama, Kazushi Sugimoto, Tadashi Sato, Mitsuo Maruyama, Masataka Sugimoto
Abstract
Following the advent of molecular assays that measure T cell receptor excision circles (TRECs) present in recent thymic emigrants, it has been conclusively shown that thymopoiesis persists in most adults, but that functional output decreases with age, influencing the maintenance of a diverse and functional T cell receptor (TCR) repertoire. Space flight has been shown to result in a variety of phenotypic and functional changes in human T cells and in the reactivation of latent viruses. While space flight has been shown to influence thymic architecture in rodents, thymopoiesis has not previously been assessed in astronauts. Here, we assessed thymopoiesis longitudinally over a 1-year period prior to and after long-term space flight (median duration, 184 days) in 16 astronauts. While preflight assessments of thymopoiesis remained quite stable in individual astronauts, we detected significant suppression of thymopoiesis in all subjects upon return from space flight. We also found significant increases in urine and plasma levels of endogenous glucocorticoids coincident with the suppression of thymopoiesis. The glucocorticoid induction and thymopoiesis suppression were transient, and they normalized shortly after return to Earth. This is the first report to our knowledge to prospectively demonstrate a significant change in thymopoiesis in healthy individuals in association with a defined physiologic emotional and physical stress event. These results suggest that suppression of thymopoiesis has the potential to influence the maintenance of the TCR repertoire during extended space travel. Further studies of thymopoiesis and endogenous glucocorticoids in other stress states, including illness, are warranted.
Authors
Cara L. Benjamin, Raymond P. Stowe, Lisa St. John, Clarence F. Sams, Satish K. Mehta, Brian E. Crucian, Duane L. Pierson, Krishna V. Komanduri
Abstract
Osteoarthritis (OA) of spine (facet joints [FJs]) is one of the major causes of severe low back pain and disability worldwide. The degeneration of facet cartilage is a hallmark of FJ OA. However, endogenous mechanisms that initiate degeneration of facet cartilage are unknown, and there are no disease-modifying therapies to stop FJ OA. In this study, we have identified microRNAs (small noncoding RNAs) as mediators of FJ cartilage degeneration. We first established a cohort of patients with varying degrees of facet cartilage degeneration (control group: normal or mild facet cartilage degeneration; FJ OA group: moderate to severe facet cartilage degeneration) and then screened 2,100 miRNAs and identified 2 miRNAs (miR-181a-5p and miR-4454) that were significantly elevated in FJ OA cartilage compared with control facet cartilage. We further explored their role, function, and signaling mechanisms using computational, in vitro functional, and in vivo studies. We specifically indicate that miR-181a-5p and miR-4454 are involved in promoting inflammatory, catabolic, and cell death activity in FJ chondrocytes. This is the first report to our knowledge that identifies miR-181a-5p and miR-4454 as mediators of cartilage degeneration in FJs and potential therapeutic targets for stopping cartilage degeneration.
Authors
Akihiro Nakamura, Y. Raja Rampersaud, Anirudh Sharma, Stephen J. Lewis, Brian Wu, Poulami Datta, Kala Sundararajan, Helal Endisha, Evgeny Rossomacha, Jason S. Rockel, Igor Jurisica, Mohit Kapoor
Abstract
High-grade serous ovarian carcinoma (HGS-OvCa) harbors p53 mutations and can originate from the epithelial cell compartment of the fallopian tube fimbriae. From this site, neoplastic cells detach, survive in the peritoneal cavity, and form cellular clusters that intercalate into the mesothelium to form ovarian and peritoneal masses. To examine the contribution of mutant p53 to phenotypic alterations associated with HGS-OvCA, we developed live-cell microscopy assays that recapitulate these early events in cultured fallopian tube nonciliated epithelial (FNE) cells. Expression of stabilizing mutant variants of p53, but not depletion of endogenous wild-type p53, in FNE cells promoted survival and cell-cell aggregation under conditions of cell detachment, leading to the formation of cell clusters with mesothelium-intercalation capacity. Mutant p53R175H-induced phenotypes were dependent on fibronectin production, α5β1 fibronectin receptor engagement, and
Authors
Marcin P. Iwanicki, Hsing-Yu Chen, Claudia Iavarone, Ioannis K. Zervantonakis, Taru Muranen, Marián Novak, Tan A. Ince, Ronny Drapkin, Joan S. Brugge
Abstract
Airway and/or lung remodeling, involving exaggerated extracellular matrix (ECM) protein deposition, is a critical feature common to pulmonary diseases including chronic obstructive pulmonary disease (COPD), asthma, and idiopathic pulmonary fibrosis (IPF). Fibulin-1 (Fbln1), an important ECM protein involved in matrix organization, may be involved in the pathogenesis of these diseases. We found that Fbln1 was increased in COPD patients and in cigarette smoke–induced (CS-induced) experimental COPD in mice. Genetic or therapeutic inhibition of
Authors
Gang Liu, Marion A. Cooley, Andrew G. Jarnicki, Alan C-Y. Hsu, Prema M. Nair, Tatt Jhong Haw, Michael Fricker, Shaan L. Gellatly, Richard Y. Kim, Mark D. Inman, Gavin Tjin, Peter A.B. Wark, Marjorie M. Walker, Jay C. Horvat, Brian G. Oliver, W. Scott Argraves, Darryl A. Knight, Janette K. Burgess, Philip M. Hansbro
Abstract
Pancreatic ductal adenocarcinoma (Pdac) is a malignancy with a poor prognosis due to difficulties in early detection. Although promising biomarkers are increasingly reported, such methods are not yet easy to apply clinically, mainly due to their low reproducibility or technical difficulties. In this study, we developed a convenient and sensitive method for quantifying aberrantly expressed satellite repeat RNAs in sera, which can be used to efficiently detect patients with Pdac. Here, we introduce a Tandem Repeat Amplification by nuclease Protection (TRAP) method combined with droplet digital PCR (ddPCR) to detect human satellite II (HSATII) RNAs, which are specifically expressed in human Pdacs at greater levels than normal tissues but are difficult to measure due to their repetitive sequences and irregularities. HSATII RNA core sequence levels in sera were significantly higher in Pdac patients compared with noncancer patients (median copy number: 14.75 and 3.17 per μl in the training set and 17.35 and 2.9 in the validation set, respectively). In addition, patients with intraductal papillary mucinous neoplasm (IPMN), a precancerous lesion of Pdac, could also be efficiently detected. This method can be routinely applied to screen patients with Pdac and high-risk patients, facilitating the development of preventive medicine for this disease.
Authors
Takahiro Kishikawa, Motoyuki Otsuka, Takeshi Yoshikawa, Motoko Ohno, Keisuke Yamamoto, Natsuyo Yamamoto, Ai Kotani, Kazuhiko Koike
Abstract
Mst1 is a central Ser-Thr kinase in the Hippo pathway, which promotes apoptosis and inhibits cell proliferation. We have shown previously that, in cardiomyocytes, oxidative stress activates Mst1 at mitochondria, where Mst1 phosphorylates Bcl-xL at Ser14, inducing dissociation of Bcl-xL from Bax and thereby promoting apoptosis. However, the functional significance of Ser14 phosphorylation of endogenous Bcl-xL in vivo remains elusive. We generated knockin (KI) mice in which Ser14 of Bcl-xL is replaced with Ala. KI mice were born at the expected Mendelian ratio, and adult KI mice exhibited normal cardiac morphology and function at baseline. However, KI mice were protected from myocardial ischemia/reperfusion (I/R) injury and exhibited reduced cardiomyocyte apoptosis. Although suppression of endogenous Mst1 also reduced I/R injury, there was no additive protective effect when Mst1 was inhibited in KI mice. The development of dilated cardiomyopathy induced by cardiac-specific overexpression of Mst1 was also ameliorated in KI mice. Lats2 and YAP, two other key components of the Hippo pathway, were not affected in KI mice. These results suggest that Ser14 phosphorylation of Bcl-xL plays an essential role in mediating both cardiomyocyte apoptosis and myocardial injury by acting as a key downstream mediator of Mst1 independently of the canonical Hippo pathway.
Authors
Michinari Nakamura, Peiyong Zhai, Dominic P. Del Re, Yasuhiro Maejima, Junichi Sadoshima
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