Biology subjects

Fleming, T.

Publications and source records attributed to Fleming, T..

4 recordsLinked to original sources

bioRxiv2021

IGFBP2 protects against pulmonary fibrosis through inhibiting P21-mediated senescence

Accumulation of senescent cells contributes to age related diseases including idiopathic pulmonary fibrosis (IPF). Insulin-like growth factor binding proteins (IGFBPs) are evolutionarily conserved proteins that play a vital role in many biological processes. Overall, little is known about the functions of IGFBP2 in the epigenetic regulation of cellular senescence and pulmonary fibrosis. Here, we show that Igfbp2 expression was significantly downregulated at both mRNA and protein levels in a low-dose bleomycin-induced pulmonary fibrosis model of aged mice. Using the reduced representation of bisulfite sequencing technique, we demonstrated Igfbp2 downregulation is attributed to DNA methylation of CpG islands in fibrotic lungs of aged mice. Furthermore, Igfbp2 siRNA knockdown increased both P53 and P21 protein levels in mouse lung epithelial cells exposed to hypoxia treatment. Lentiviral mediated expression of Igfb2 decreased P21 protein levels and significantly reduced beta galactosidase activity in mouse lung epithelial cells challenged with a senescent drug (atazanavir) and hypoxia treatments. Using the RT2 Profiler PCR Array, we found that P21, PAI-1, IRF-5 and IRF-7, important regulators of senescence pathway, were significantly downregulated specifically in type-II alveolar epithelial cells (AECs) of aged human-Igfbp2 transgenic mice after bleomycin challenge. Finally, transgenic expression of human-Igfbp2 in type-II AECs from aged bleomycin challenged mice significantly decreased senescent associated secretory phenotype factors and also reduced extracellular matrix markers compared to aged wild-type mice challenged with bleomycin injury. Collectively, these findings reveal that epigenetic repression of Igfbp2 promotes pulmonary fibrosis and that restoring IGFBP2 in fibrotic lungs could prove effective in IPF treatment.

molecular biology↗

bioRxiv2020

Etv5 is not required for Schwann cell development but is required to regulate the Schwann cell response to peripheral nerve injury

Schwann cells are the principal glial cells of the peripheral nervous system, and their development into myelinating glia is critically dependent on MEK/ERK signaling. Ets-domain transcription factors (Etv1, Etv4, Etv5) are common downstream effectors of MEK/ERK signalling, but so far, only Etv1 has been ascribed a role in Schwann cell development, and only in non-myelinating cells. Here, we examined the role of Etv5, which is expressed in Schwann cell precursors, including neural crest cells and satellite glia, in Schwann cell lineage development. We analysed Etv5tm1Kmm mutants (designated Etv5-/-) at embryonic days (E) 12.5, E15.5 and E18.5, focusing on dorsal root ganglia. At these embryonic stages, satellite glia (glutamine synthetase) and Schwann cell markers, including transcriptional regulators (Sox10, Sox9, Tfap2a, Pou3f1) and non-transcription factors (Ngfr, BFABP, GFAP), were expressed in the DRG of wild-type and Etv5-/- embryos. Furthermore, by E18.5, quantification of Sox10+ Schwann cells and NeuN+ neurons revealed that these cells were present in normal numbers in the Etv5-/- dorsal root ganglia. We next performed peripheral nerve injuries at postnatal day 21, revealing that Etv5-/- mice had an enhanced injury response, generating more Sox10+ Schwann cells compared to wild-type animals at five days post-injury. Thus, while Etv5 is not required for Schwann cell development, possibly due to genetic redundancy with Etv1 and/or Etv4, Etv5 is an essential negative regulator of the peripheral nerve injury repair response. SIGNIFICANCE STATEMENTOur study sought to determine whether the ets domain transcription factor, Etv5, plays a role in regulating Schwann cell development and nerve repair. By using an embryonically and postnatally viable hypomorphic Etv5 mutant allele, we demonstrated that Etv5 is not required for the development of Schwann cells or other neural crest derivatives in the dorsal root ganglia, including satellite glia and neurons. Surprisingly, loss of Etv5 had a direct impact on the Schwann cell repair response post-injury, resulting in more Schwann cells populating the distal injured nerve site compared to wild-type animals. Thus, this work describes for the first time a role for Etv5 in regulating the Schwann cell repair response after peripheral nerve injury.

developmental biology↗

bioRxiv2020

SMPD3-mediated extracellular vesicle biogenesis inhibits oligodendroglioma growth

Isocitrate dehydrogenase (IDH) mutant gliomas, including oligodendroglioma (IDH-O) and astrocytoma (IDH-A), have signature slow-growth rates that are poorly understood. Here, we reveal that SMPD3, a ceramide-producing sphingomyelinase implicated as a tumor suppressor gene and involved in extracellular vesicle biogenesis, suppresses IDH-mutant tumor growth via autocrine and paracrine actions. In patients with IDH-mutant gliomas, higher SMPD3 expression levels correlate with longer survival, consistent with ceramide acting as an anti-oncometabolite. SMPD3 knock-down in patient-derived IDH-O cells enhances proliferation cell-autonomously in 2D-culture and 3D-human cerebral organoids, and accelerates tumor growth in mouse orthotopic xenografts. Supporting paracrine actions, IDH-O-derived extracellular vesicles, enriched in ribosomal proteins, induce astrocytic death in vitro. Furthermore, non-neoplastic glia in IDH-O tumors proliferate abnormally yet undergo apoptosis, concomitant with the acquisition of a translation-enriched transcriptional signature by tumor-associated oligodendrocytes. SMPD3 thus suppresses IDH-mutant glioma growth cell-autonomously and phenotypically alters normal glia via extracellular vesicle biogenesis and paracrine actions.

cancer biology↗

bioRxiv2020

Phosphorylation of Threonine 107 by Calcium/Calmodulin dependent Kinase II δ Regulates the Detoxification Efficiency and Proteomic Integrity of Glyoxalase 1

The glyoxalase system is a ubiquitously expressed enzyme system with narrow substrate specificity and is responsible for the detoxification of harmful methylglyoxal (MG), a spontaneous by-product of energy metabolism. Glyoxalase 1 (Glo1) is the first and therefore rate limiting enzyme of this protective system. In this study we were able to show that a phosphorylation of threonine-107 in the Glo1 protein, mediated by Ca2+/Calmodulin-dependent Kinase II delta (CamKII{delta}), is associated with elevated catalytic efficiency of Glo1. In fact, Michaelis-Menten kinetics of Glo1 mutants revealed that a permanent phosphorylation of Glo1 was associated with increased Vmax (1.23 {micro}mol/min/mg) and decreased Km (0.19 mM HTA), whereas the non-phosphorylatable Glo1 showed significantly lower Vmax (0.66 {micro}mol/min/mg) and increased Km (0.31 mM HTA). This was also confirmed with human recombinant Glo1 (Vmax (Glo1phos) = 999 {micro}mol/min/mg; Km (Glo1phos) = 0.09 mM HTA vs. Vmax (Glo1red) = 497 {micro}mol/min/mg; Km (Glo1red) = 0.12 mM HTA). Additionally, proteasomal degradation of non-phosphorylated Glo1 via ubiquitination occurred more rapidly as compared to native Glo1. The absence of the responsible kinase CamKII{delta} was associated with poor MG detoxification capacity and decreased protein content of Glo1 in a murine CamKII{delta} knock-out model. Furthermore, this regulatory mechanism is also related to an altered Glo1 status in cancer, diabetes and during aging. In summary, phosphorylation of threonine-107 in the Glo1 protein by CamKII{delta} is a quick and precise mechanism regulating Glo1 activity.

molecular biology↗