Biology subjects

Chapple, J. P.

Publications and source records attributed to Chapple, J. P..

4 recordsLinked to original sources

bioRxiv2025

Phaeochromocytomas and paragangliomas harbour tumour-initiating SOX2+ stem cells

Phaeochromocytomas (PCCs) and paragangliomas (PGLs), are rare neuroendocrine tumours that arise in the neural crest (NC)-derived adrenal medulla and the paraganglia, respectively. Approximately 10%-15% of patients with PCCs and 35%-40% with PGLs go on to develop metastatic disease, leading to a reported median overall survival of 7 years. The development of prognostic markers and subsequent personal therapeutic strategies are hindered by a lack of understanding of tumourigenesis. In other organs, cells with stem-like properties are at the root of tumour initiation and maintenance, due to their ability to self- renew and give rise to differentiated cells. We have recently shown that, in the human adrenal, a subset of sustentacular cells, endowed with a support role, are in fact SOX2+ postnatal adrenomedullary stem cells, that are specified along the neural crest migratory route. In this study, we intended to determine if SOX2+ cells in PCCs and PGLs can behave as tumour-initiating stem cells. Using expression and transcriptomic studies, we demonstrate the presence of SOX2/SOX2-expressing cells across a broad range of PCCs and PGLs, irrespective of tumour aggressiveness, location, and causative mutation. In silico analyses reveal the co-expression of SOX2 and chromaffin cell markers in the tumour, and the active proliferation of these double-positive cells. Isolation of these cells in vitro in stem cell-promoting media, and their xenotransplantation on chicken chorioallantoic membranes, demonstrates that they have the potential to expand and metastasise in ovo, supporting their potential as tumour-initiating cells.

cancer biology↗

bioRxiv2022

AlphaFold predicted structure of the Hsp90-like domains of the neurodegeneration linked protein sacsin reveals key residues for ATPase activity

The ataxia-linked protein sacsin has three regions of partial homology to Hsp90s N-terminal ATP binding domain. Although a crystal structure for the Hsp90-like domain of sacsin has been reported the precise molecular interactions required for ATP-binding and hydrolysis are unclear. To better understand how sacsin may function as an ATPase we utilized an AlphaFold predicted structure of its Hsp90-like domain. Superimposition onto Hsp90, and other modelling approaches, have resulted in novel insights into sacsins structure. These encompass identification of residues within the sacsin Hsp90-like domains that are required for ATP binding and hydrolysis, including the catalytic arginine residues equivalent to that of the Hsp90 middle domain. Importantly, our analysis allows comparison of the Hsp90 middle domain with corresponding sacsin regions and has identified that sacsin has a shorter lid segment than the N-terminal domain of Hsp90. We also speculate, from a structural viewpoint, why ATP competitive inhibitors of Hsp90 do not appear to affect sacsin. Together our analysis supports the hypothesis that sacsins function is ATP-driven and would be consistent with it having a role as a molecular chaperone. We propose that the SR1 regions of sacsin be renamed as HSP-NRD (Hsp90 N-Terminal Repeat Domain; residues 84-324) and the fragment immediately after as HSP-MRD (Hsp90 Middle Repeat Domain; residues 325-518).

molecular biology↗

bioRxiv2021

The ataxia protein sacsin is required for integrin trafficking and synaptic organization

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is caused by mutations in SACS, which manifest as a childhood-onset cerebellar ataxia. Cellular ARSACS phenotypes include mitochondrial dysfunction, intermediate filament (IF) disorganization, and loss of Purkinje neurons. It is unclear how the loss of SACS causes these deficits, or why they manifest as cerebellar ataxia. We employed a multi-omics approach to characterize molecular and cellular deficiencies in SACS knockout (KO) cells. We identified alterations in microtubule structure and dynamics, protein trafficking, and mislocalization of synaptic and focal adhesion proteins. Targeting PTEN, a negative regulator of focal adhesions, rescued several cellular phenotypes in SACS KO cells. We found sacsin interacts with proteins implicated in vesicle transport, including HSP proteins, and interactions between structural and cell adhesion proteins were diminished in SACS KO cells. In all, this study suggests that trafficking and localization of synaptic adhesion proteins is a causal molecular deficiency in ARSACS.

cell biology↗

bioRxiv2019

GATA3 controls mitochondrial biogenesis in primary human CD4+ T cells during DNA damage

Introductory paragraphGATA binding protein 3 (GATA3) has traditionally been regarded as a lineage-specific transcription factor that drives the differentiation of CD4+ T helper (Th) 2 cells. However, increasing evidence shows that GATA3 is involved in a myriad of processes such as immune regulation, proliferation and maintenance in other T cell and non-T cell lineages. We show here a previously unknown mechanism utilized by CD4+ T cells to increase mitochondrial mass in response to DNA damage through the binding of GATA3, AMP-activated protein kinase (AMPK), peroxisome-proliferator-activated receptor {gamma} co-activator-1 (PGC1), nuclear factor erythroid 2-related factor 2 (NRF2) and superoxide dismutase 3 (SOD3) to the DNA damage repair (DDR) component ATR. These findings extend the pleotropic nature of GATA3 and highlight the potential for GATA3-targeted cell manipulation for clinical interventions.

immunology↗