ISGylation drives basal breast tumour progression by promoting EGFR recycling and Akt signalling

ISG15 is an ubiquitin-like modifier that is associated with reduced survival rates in breast cancer patients. The mechanism by which ISG15 achieves this however remains elusive. We demonstrate that modification of Rab GDP-Dissociation Inhibitor Beta (GDI2) by ISG15 (ISGylation) alters endocytic recycling of the EGF receptor (EGFR) in non-interferon stimulated cells using CRISPR-knock out models for ISGylation. By regulating EGFR trafficking, ISGylation enhances EGFR recycling and sustains Akt-signalling. We further show that Akt signalling positively correlates with levels of ISG15 and its E2-ligase in basal breast cancer cohorts, confirming the link between ISGylation and Akt signalling in human tumours. Persistent and enhanced Akt activation explains the more aggressive tumour behaviour observed in human breast cancers. We show that ISGylation can act as a driver of tumour progression rather than merely being a bystander.

Utilizing an Animal Model to Identify Brain Neurodegeneration-Related Biomarkers in Aging

Glycine N-methyltransferase (GNMT) regulates S-adenosylmethionine (SAMe), a methyl donor in methylation. Over-expressed SAMe may cause neurogenic capacity reduction and memory impairment. GNMT knockout mice (GNMT-KO) was applied as an experimental model to evaluate its effect on neurons. In this study, proteins from brain tissues were studied using proteomic approaches, Haemotoxylin and Eosin staining, immunohistochemistry, Western blotting, and ingenuity pathway analysis. The expression of Receptor-interacting protein 1(RIPK1) and Caspase 3 were up-regulated and activity-dependent neuroprotective protein (ADNP) was down-regulated in GNMT-KO mice regardless of the age. Besides, proteins related to neuropathology, such as excitatory amino acid transporter 2, calcium/calmodulin-dependent protein kinase type II subunit alpha, and Cu-Zn superoxide dismutase were found only in the group of aged wild-type mice; 4-aminobutyrate amino transferase, limbic system-associated membrane protein, sodium- and chloride-dependent GABA transporter 3 and ProSAAS were found only in the group of young GNMT-KO mice and are related to function of neurons; serum albumin and Rho GDP dissociation inhibitor 1 were found only in the group of aged GNMT-KO mice and are connected to neurodegenerative disorders. With proteomic analyses, a pathway involving Gonadotropin-releasing hormone (GnRH) signal was found to be associated with aging. The GnRH pathway could provide additional information on the mechanism of aging and non-aging related neurodegeneration, and these protein markers may be served in developing future therapeutic treatments to ameliorate aging and prevent diseases.

GDP dissociation inhibitor 1 is a differentially expressed gene in brain metastatic human breast cancer.

Metastasis to the brain is a clinical problem in patients with breast cancer (1-3). We mined published microarray data (4, 5) to compare primary and metastatic tumor transcriptomes for the discovery of genes associated with brain metastasis in humans with metastatic breast cancer. We found that GDP dissociation inhibitor 1, encoded by GDI1, was among the genes whose expression was most different in the brain metastases of patients with metastatic breast cancer as compared to primary tumors of the breast. GDI1 mRNA was present at increased quantities in brain metastatic tissues as compared to primary tumors of the breast. Importantly, expression of GDI1 in primary tumors was significantly correlated with patient distant metastasis-free survival. Modulation of GDI1 expression may be relevant to the biology by which tumor cells metastasize from the breast to the brain in humans with metastatic breast cancer.

A toxic palmitoylation on Cdc42 drives a severe autoinflammatory syndrome

BackgroundAutoinflammatory diseases (AID) result from dysregulation of the first lines of innate immune responses. Recently, development of high throughput genome sequencing technology led to the rapid emergence of important knowledge in the genetic field. About 20 genes have been identified so far in monogenic forms of distinct AID. However, 70-90 % of patients with AID remain without genetic diagnosis.ObjectiveWe report the identification and characterization of a mutation in the C-terminal region of the Rho GTPase Cdc42 in a patient presenting a severe autoinflammatory phenotype.MethodsWe have analyzed the consequences of the mutation on the subcellular localization of the Cdc42 protein using imaging techniques. Molecular studies were performed using proteomic and biochemical experiments to provide mechanistic bases of the observed defects. Functional assays were also conducted using flow cytometry and cytokine production measurements.ResultsWe show that mutant Cdc42 is trapped in the Golgi apparatus due to the aberrant addition of a palmitate that both enhances the interaction of mutant Cdc42 with Golgi membranes and inhibit its extraction by GDP dissociation inhibitor (GDI), thus impairing its cytosol/membrane shuttling. At the functional level, mutant Cdc42 fails to sustain actin filaments polymerization and induces an exacerbated profile of pro-inflammatory cytokine production due to increased NF-κB activation.ConclusionsOur study now provides a molecular explanation for mutations that have been identified recently in our AID patient and others in the C-terminal part of Cdc42. Mutations located in this region of Cdc42 impair the intracellular localization of Cdc42, preventing its interaction with the plasma membrane. Thus, our results definitively link mutations in the CDC42 gene to a complex immune-hemato-autoinflammatory phenotype in humans.

ISGylation drives basal breast tumour progression by promoting EGFR recycling and Akt signalling

ABSTRACTISG15 is an ubiquitin-like modifier that is associated with reduced survival rates in breast cancer patients. However, the mechanism by which ISG15 achieves this remains elusive. We demonstrate that modification of Rab GDP-Dissociation Inhibitor Beta (GDI2) by ISG15 (ISGylation) alters endocytic recycling of the EGF receptor (EGFR). By regulating EGFR trafficking, ISGylation sustains Akt-signalling in vitro and in vivo. Persistent and enhanced Akt activation explains the more aggressive tumour behaviour observed in animal models and human breast cancers. We show that ISGylation can act as driver of tumour progression rather than merely being a marker of it.