CKAP4 is a Dickkopf1 receptor and is involved in tumor progression

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Abstract

Dickkopf1 (DKK1) is a secretory protein that antagonizes oncogenic Wnt signaling by binding to the Wnt coreceptor low-density lipoprotein receptor–related protein 6 (LRP6). DKK1 may also regulate its own signaling to promote cancer cell proliferation, but the mechanism is not understood. Here, we identified cytoskeleton-associated protein 4 (CKAP4) as a DKK1 receptor and evaluated CKAP4-mediated DKK1 signaling in cancer cell proliferation. We determined that DKK1 binds CKAP4 and LRP6 with similar affinity but interacts with these 2 receptors with different cysteine-rich domains. DKK1 induced internalization of CKAP4 in a clathrin-dependent manner, further supporting CKAP4 as a receptor for DKK1. DKK1/CKAP4 signaling activated AKT by forming a complex between the proline-rich domain of CKAP4 and the Src homology 3 domain of PI3K, resulting in proliferation of normal cells and cancer cells. Expression of DKK1 and CKAP4 was frequent in tumor lesions of human pancreatic and lung cancers, and simultaneous expression of both proteins in patient tumors was negatively correlated with prognosis and relapse-free survival. An anti-CKAP4 antibody blocked the binding of DKK1 to CKAP4, suppressed AKT activity in a human cancer cell line, and attenuated xenograft tumor formation in immunodeficient mice. Together, our results suggest that CKAP4 is a potential therapeutic target for cancers that express both DKK1 and CKAP4.

Authors

Hirokazu Kimura, Katsumi Fumoto, Kensaku Shojima, Satoshi Nojima, Yoshihito Osugi, Hideo Tomihara, Hidetoshi Eguchi, Yasushi Shintani, Hiroko Endo, Masahiro Inoue, Yuichiro Doki, Meinoshin Okumura, Eiichi Morii, Akira Kikuchi

Schwann cells induce cancer cell dispersion and invasion

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Abstract

Nerves enable cancer progression, as cancers have been shown to extend along nerves through the process of perineural invasion, which carries a poor prognosis. Furthermore, the innervation of some cancers promotes growth and metastases. It remains unclear, however, how nerves mechanistically contribute to cancer progression. Here, we demonstrated that Schwann cells promote cancer invasion through direct cancer cell contact. Histological evaluation of murine and human cancer specimens with perineural invasion uncovered a subpopulation of Schwann cells that associates with cancer cells. Coculture of cancer cells with dorsal root ganglion extracts revealed that Schwann cells direct cancer cells to migrate toward nerves and promote invasion in a contact-dependent manner. Upon contact, Schwann cells induced the formation of cancer cell protrusions in their direction and intercalated between the cancer cells, leading to cancer cell dispersion. The formation of these processes was dependent on Schwann cell expression of neural cell adhesion molecule 1 (NCAM1) and ultimately promoted perineural invasion. Moreover, NCAM1-deficient mice showed decreased neural invasion and less paralysis. Such Schwann cell behavior reflects normal Schwann cell programs that are typically activated in nerve repair but are instead exploited by cancer cells to promote perineural invasion and cancer progression.

Authors

Sylvie Deborde, Tatiana Omelchenko, Anna Lyubchik, Yi Zhou, Shizhi He, William F. McNamara, Natalya Chernichenko, Sei-Young Lee, Fernando Barajas, Chun-Hao Chen, Richard L. Bakst, Efsevia Vakiani, Shuangba He, Alan Hall, Richard J. Wong

Lymphatic endothelial cells are a replicative niche for Mycobacterium tuberculosis

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Abstract

In extrapulmonary tuberculosis, the most common site of infection is within the lymphatic system, and there is growing recognition that lymphatic endothelial cells (LECs) are involved in immune function. Here, we identified LECs, which line the lymphatic vessels, as a niche for Mycobacterium tuberculosis in the lymph nodes of patients with tuberculosis. In cultured primary human LECs (hLECs), we determined that M. tuberculosis replicates both in the cytosol and within autophagosomes, but the bacteria failed to replicate when the virulence locus RD1 was deleted. Activation by IFN-γ induced a cell-autonomous response in hLECs via autophagy and NO production that restricted M. tuberculosis growth. Thus, depending on the activation status of LECs, autophagy can both promote and restrict replication. Together, these findings reveal a previously unrecognized role for hLECs and autophagy in tuberculosis pathogenesis and suggest that hLECs are a potential niche for M. tuberculosis that allows establishment of persistent infection in lymph nodes.

Authors

Thomas R. Lerner, Cristiane de Souza Carvalho-Wodarz, Urska Repnik, Matthew R.G. Russell, Sophie Borel, Collin R. Diedrich, Manfred Rohde, Helen Wainwright, Lucy M. Collinson, Robert J. Wilkinson, Gareth Griffiths, Maximiliano G. Gutierrez

Xenotropic retrovirus Bxv1 in human pancreatic β cell lines

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Abstract

It has been reported that endogenous retroviruses can contaminate human cell lines that have been passaged as xenotransplants in immunocompromised mice. We previously developed and described 2 human pancreatic β cell lines (EndoC-βH1 and EndoC-βH2) that were generated in this way. Here, we have shown that B10 xenotropic virus 1 (Bxv1), a xenotropic endogenous murine leukemia virus (MuLV), is present in these 2 recently described cell lines. We determined that Bxv1 was also present in SCID mice that were used for in vivo propagation of EndoC-βH1/2 cells, suggesting that contamination occurred during xenotransplantation. EndoC-βH1/2 cells released Bxv1 particles that propagated to human 293T and Mus dunni cells. Mobilization assays demonstrated that Bxv1 transcomplements defective MuLV-based retrovectors. In contrast, common rodent β cell lines, rat INS-1E and RIN-5F cells and mouse MIN6 and βTC3 cells, displayed either no or extremely weak xenotropic helper activity toward MuLV-based retrovectors, although xenotropic retrovirus sequences and transcripts were detected in both mouse cell lines. Bxv1 propagation from EndoC-βH1/2 to 293T cells occurred only under optimized conditions and was overall poorly efficient. Thus, although our data imply that MuLV-based retrovectors should be cautiously used in EndoC-βH1/2 cells, our results indicate that an involuntary propagation of Bxv1 from these cells can be easily avoided with good laboratory practices.

Authors

Jeannette S. Kirkegaard, Philippe Ravassard, Signe Ingvarsen, Marc Diedisheim, Emilie Bricout-Neveu, Mads Grønborg, Thomas Frogne, Raphael Scharfmann, Ole D. Madsen, Claude Rescan, Olivier Albagli

Blocking mitochondrial calcium release in Schwann cells prevents demyelinating neuropathies

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Abstract

Schwann cells produce myelin sheath around peripheral nerve axons. Myelination is critical for rapid propagation of action potentials, as illustrated by the large number of acquired and hereditary peripheral neuropathies, such as diabetic neuropathy or Charcot-Marie-Tooth diseases, that are commonly associated with a process of demyelination. However, the early molecular events that trigger the demyelination program in these diseases remain unknown. Here, we used virally delivered fluorescent probes and in vivo time-lapse imaging in a mouse model of demyelination to investigate the underlying mechanisms of the demyelination process. We demonstrated that mitochondrial calcium released by voltage-dependent anion channel 1 (VDAC1) after sciatic nerve injury triggers Schwann cell demyelination via ERK1/2, p38, JNK, and c-JUN activation. In diabetic mice, VDAC1 activity was altered, resulting in a mitochondrial calcium leak in Schwann cell cytoplasm, thereby priming the cell for demyelination. Moreover, reduction of mitochondrial calcium release, either by shRNA-mediated VDAC1 silencing or pharmacological inhibition, prevented demyelination, leading to nerve conduction and neuromuscular performance recovery in rodent models of diabetic neuropathy and Charcot-Marie-Tooth diseases. Therefore, this study identifies mitochondria as the early key factor in the molecular mechanism of peripheral demyelination and opens a potential opportunity for the treatment of demyelinating peripheral neuropathies.

Authors

Sergio Gonzalez, Jade Berthelot, Jennifer Jiner, Claire Perrin-Tricaud, Ruani Fernando, Roman Chrast, Guy Lenaers, Nicolas Tricaud

GLP-1 stimulates insulin secretion by PKC-dependent TRPM4 and TRPM5 activation

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Abstract

Strategies aimed at mimicking or enhancing the action of the incretin hormone glucagon-like peptide 1 (GLP-1) therapeutically improve glucose-stimulated insulin secretion (GSIS); however, it is not clear whether GLP-1 directly drives insulin secretion in pancreatic islets. Here, we examined the mechanisms by which GLP-1 stimulates insulin secretion in mouse and human islets. We found that GLP-1 enhances GSIS at a half-maximal effective concentration of 0.4 pM. Moreover, we determined that GLP-1 activates PLC, which increases submembrane diacylglycerol and thereby activates PKC, resulting in membrane depolarization and increased action potential firing and subsequent stimulation of insulin secretion. The depolarizing effect of GLP-1 on electrical activity was mimicked by the PKC activator PMA, occurred without activation of PKA, and persisted in the presence of PKA inhibitors, the K_ATP channel blocker tolbutamide, and the L-type Ca²⁺ channel blocker isradipine; however, depolarization was abolished by lowering extracellular Na⁺. The PKC-dependent effect of GLP-1 on membrane potential and electrical activity was mediated by activation of Na⁺-permeable TRPM4 and TRPM5 channels by mobilization of intracellular Ca²⁺ from thapsigargin-sensitive Ca²⁺ stores. Concordantly, GLP-1 effects were negligible in Trpm4 or Trpm5 KO islets. These data provide important insight into the therapeutic action of GLP-1 and suggest that circulating levels of this hormone directly stimulate insulin secretion by β cells.

Authors

Makoto Shigeto, Reshma Ramracheya, Andrei I. Tarasov, Chae Young Cha, Margarita V. Chibalina, Benoit Hastoy, Koenraad Philippaert, Thomas Reinbothe, Nils Rorsman, Albert Salehi, William R. Sones, Elisa Vergari, Cathryn Weston, Julia Gorelik, Masashi Katsura, Viacheslav O. Nikolaev, Rudi Vennekens, Manuela Zaccolo, Antony Galione, Paul R.V. Johnson, Kohei Kaku, Graham Ladds, Patrik Rorsman

PRMT1-mediated methylation of the EGF receptor regulates signaling and cetuximab response

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Abstract

Posttranslational modifications to the intracellular domain of the EGFR are known to regulate EGFR functions; however, modifications to the extracellular domain and their effects remain relatively unexplored. Here, we determined that methylation at R198 and R200 of the EGFR extracellular domain by protein arginine methyltransferase 1 (PRMT1) enhances binding to EGF and subsequent receptor dimerization and signaling activation. In a mouse orthotopic colorectal cancer xenograft model, expression of a methylation-defective EGFR reduced tumor growth. Moreover, increased EGFR methylation sustained signaling activation and cell proliferation in the presence of the therapeutic EGFR monoclonal antibody cetuximab. In colorectal cancer patients, EGFR methylation level also correlated with a higher recurrence rate after cetuximab treatment and reduced overall survival. Together, these data indicate that R198/R200 methylation of the EGFR plays an important role in regulating EGFR functionality and resistance to cetuximab treatment.

Authors

Hsin-Wei Liao, Jung-Mao Hsu, Weiya Xia, Hung-Ling Wang, Ying-Nai Wang, Wei-Chao Chang, Stefan T. Arold, Chao-Kai Chou, Pei-Hsiang Tsou, Hirohito Yamaguchi, Yueh-Fu Fang, Hong-Jen Lee, Heng-Huan Lee, Shyh-Kuan Tai, Mhu-Hwa Yang, Maria P. Morelli, Malabika Sen, John E. Ladbury, Chung-Hsuan Chen, Jennifer R. Grandis, Scott Kopetz, Mien-Chie Hung

Ciliopathy proteins regulate paracrine signaling by modulating proteasomal degradation of mediators

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Abstract

Cilia are critical mediators of paracrine signaling; however, it is unknown whether proteins that contribute to ciliopathies converge on multiple paracrine pathways through a common mechanism. Here, we show that loss of cilopathy-associated proteins Bardet-Biedl syndrome 4 (BBS4) or oral-facial-digital syndrome 1 (OFD1) results in the accumulation of signaling mediators normally targeted for proteasomal degradation. In WT cells, several BBS proteins and OFD1 interacted with proteasomal subunits, and loss of either BBS4 or OFD1 led to depletion of multiple subunits from the centrosomal proteasome. Furthermore, overexpression of proteasomal regulatory components or treatment with proteasomal activators sulforaphane (SFN) and mevalonolactone (MVA) ameliorated signaling defects in cells lacking BBS1, BBS4, and OFD1, in morphant zebrafish embryos, and in induced neurons from Ofd1-deficient mice. Finally, we tested the hypothesis that other proteasome-dependent pathways not known to be associated with ciliopathies are defective in the absence of ciliopathy proteins. We found that loss of BBS1, BBS4, or OFD1 led to decreased NF-κB activity and concomitant IκBβ accumulation and that these defects were ameliorated with SFN treatment. Taken together, our data indicate that basal body proteasomal regulation governs paracrine signaling pathways and suggest that augmenting proteasomal function might benefit ciliopathy patients.

Authors

Yangfan P. Liu, I-Chun Tsai, Manuela Morleo, Edwin C. Oh, Carmen C. Leitch, Filomena Massa, Byung-Hoon Lee, David S. Parker, Daniel Finley, Norann A. Zaghloul, Brunella Franco, Nicholas Katsanis

Disrupting hedgehog and WNT signaling interactions promotes cleft lip pathogenesis

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Abstract

Cleft lip, which results from impaired facial process growth and fusion, is one of the most common craniofacial birth defects. Many genes are known to be involved in the etiology of this disorder; however, our understanding of cleft lip pathogenesis remains incomplete. In the present study, we uncovered a role for sonic hedgehog (SHH) signaling during lip fusion. Mice carrying compound mutations in hedgehog acyltransferase (Hhat) and patched1 (Ptch1) exhibited perturbations in the SHH gradient during frontonasal development, which led to hypoplastic nasal process outgrowth, epithelial seam persistence, and cleft lip. Further investigation revealed that enhanced SHH signaling restricts canonical WNT signaling in the lambdoidal region by promoting expression of genes encoding WNT inhibitors. Moreover, reduction of canonical WNT signaling perturbed p63/interferon regulatory factor 6 (p63/IRF6) signaling, resulting in increased proliferation and decreased cell death, which was followed by persistence of the epithelial seam and cleft lip. Consistent with our results, mutations in genes that disrupt SHH and WNT signaling have been identified in both mice and humans with cleft lip. Collectively, our data illustrate that altered SHH signaling contributes to the etiology and pathogenesis of cleft lip through antagonistic interactions with other gene regulatory networks, including the canonical WNT and p63/IRF6 signaling pathways.

Authors

Hiroshi Kurosaka, Angelo Iulianella, Trevor Williams, Paul A. Trainor

Assembly of the cochlear gap junction macromolecular complex requires connexin 26

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Abstract

Hereditary deafness affects approximately 1 in 2,000 children. Mutations in the gene encoding the cochlear gap junction protein connexin 26 (CX26) cause prelingual, nonsyndromic deafness and are responsible for as many as 50% of hereditary deafness cases in certain populations. Connexin-associated deafness is thought to be the result of defective development of auditory sensory epithelium due to connexion dysfunction. Surprisingly, CX26 deficiency is not compensated for by the closely related connexin CX30, which is abundantly expressed in the same cochlear cells. Here, using two mouse models of CX26-associated deafness, we demonstrate that disruption of the CX26-dependent gap junction plaque (GJP) is the earliest observable change during embryonic development of mice with connexin-associated deafness. Loss of CX26 resulted in a drastic reduction in the GJP area and protein level and was associated with excessive endocytosis with increased expression of caveolin 1 and caveolin 2. Furthermore, expression of deafness-associated CX26 and CX30 in cell culture resulted in visible disruption of GJPs and loss of function. Our results demonstrate that deafness-associated mutations in CX26 induce the macromolecular degradation of large gap junction complexes accompanied by an increase in caveolar structures.

Authors

Kazusaku Kamiya, Sabrina W. Yum, Nagomi Kurebayashi, Miho Muraki, Kana Ogawa, Keiko Karasawa, Asuka Miwa, Xueshui Guo, Satoru Gotoh, Yoshinobu Sugitani, Hitomi Yamanaka, Shioko Ito-Kawashima, Takashi Iizuka, Takashi Sakurai, Tetsuo Noda, Osamu Minowa, Katsuhisa Ikeda