Human FCHO1 deficiency reveals role for clathrin-mediated endocytosis in development and function of T cells

Abstract

Clathrin-mediated endocytosis (CME) is critical for internalisation of molecules across cell membranes. The FCH domain only 1 (FCHO1) protein is key molecule involved in the early stages of CME formation. The consequences of mutations in FCHO1 in humans were unknown. We identify ten unrelated patients with variable T and B cell lymphopenia, who are homozygous for six distinct mutations in FCHO1. We demonstrate that these mutations either lead to mislocalisation of the protein or prevent its interaction with binding partners. Live-cell imaging of cells expressing mutant variants of FCHO1 provide evidence of impaired formation of clathrin coated pits (CCP). Patient T cells are unresponsive to T cell receptor (TCR) triggering. Internalisation of the TCR receptor is severely perturbed in FCHO1-deficient Jurkat T cells but can be rescued by expression of wild-type FCHO1. Thus, we discovered a previously unrecognised critical role of FCHO1 and CME during T-cell development and function in humans.

Clathrin’s life beyond 40: Connecting biochemistry with physiology and disease

“…In addition to neuronal and lymphocyte phenotypes for CLCa or CLCb depletion [15,62] and the muscle phenotypes for defective CHC splicing [33,34], mutation in the AAGAB protein affecting AP2 assembly manifests as the human skin disease punctate palmoplantar keratoderma type 1 [40] and AP1 mutations are associated with congenital enteropathy [63]. Deficiency of the CME-nucleating protein FCHO1 causes a T-lymphocyte defect [64], and loss of the assembly regulator AP180 affects murine cochlear inner hair cells [65] in addition to neuronal function, and the latter is seen for many other adaptor and assembly factor defects [66]. Interestingly, degenerative diseases in which protein aggregates (Tau or -synuclein) sequester the Hsc70 clathrin uncoating protein have phenotypes resulting from disrupted CME that can be rescued by excess Hsc70 [67,68].…”

Phenotypic Characteristics and Copy Number Variants in a Cohort of Colombian Patients with VACTERL Association

“…Autophagy is an evolutionarily conserved process in all eukaryotic organisms and plays a key role in maintaining cellular homeostasis during embryonic development and differentiation [Martinet et al, 2009;Boya et al, 2018;Levine and Kroemer, 2019]. FCHO1 is another gene involved in clathrin-mediated endocytosis and in T-cell development and function in humans [Sheu et al, 2003;Łyszkiewicz et al, 2020]. Silencing of fcho1 in zebrafish embryos causes alterations in morphogenesis [Umasankar et al, 2012].…”

Imaging vesicle formation dynamics supports the flexible model of clathrin-mediated endocytosis

“…Cells were washed with prewarmed HBSS, and Mock cells were incubated in serum-free FluoroBrite DMEM media (Gibco, A1896701), wherase CLCa-STAR overexpressing cells were incubated with serum-free FluoroBrite DMEM media supplemented with 5 μM biliverdin (co-factor for iRFP713; Cayman Chemical, 1925710), for at least 30 min. Media was then replaced with serum-free FluoroBrite DMEM media supplemented with 25 μg/ml 40 Transferrin-Alexa Fluor 568 conjugate 39 (TF-568, Thermo Fisher Scientific, T23365), and cells were incubated for 20, 15, 10, 5, and 0 min in a 37 °C. Then, 24-well dish was placed immediately on ice to stop internalization.…”