Structural insight into the Scribble PDZ domains interaction with the oncogenic Human T-cell lymphotrophic virus-1 (HTLV-1) Tax1 PBM

First published: 27 August 2022. OnlinePublScribble (Scrib) is a highly conserved cell polarity regulator that harbours potent tumour suppressor activity and plays an important role in cell migration. Dysregulation of polarity is associated with poor prognosis during viral infections. Human T-cell lymphotrophic virus-1 (HTLV-1) encodes for the oncogenic Tax1 protein, a modulator of the transcription of viral and human proteins that can cause cell cycle dysregulation as well as a loss of genomic integrity. Previous studies established that Scribble interacts with Tax1 via its C-terminal PDZ binding motif (PBM), leading to aggregation of polarity regulators and subsequent perturbation of host cell adhesion, proliferation, and signalling. Using isothermal titration calorimetry (ITC) we now show that all four PDZ domains of Scribble bind to Tax1 PBM. We then determined crystal structures of Scribble PDZ1, PDZ2 and PDZ3 domains bound to Tax1 PBM. Our findings establish a structural basis for Tax1 mediated subversion of Scribble mediated cell polarity signalling and provide the platform for mechanistic studies to examine Tax1 induced mislocalisation of Scribble and the associated changes in cellular architecture and subsequent tumorigenesis.Airah Javorsky, Janesha C. Maddumage, Emily R. R. Mackie, Tatiana P. Soares da Costa, Patrick O. Humbert and Marc Kvansaku

T cell shape is orchestrated by PDZ-containing proteins: Parallels with epithelial polarity

The Cre/loxP system is facilitates excision of DNA sequences located between two loxP sites by the Cre recombinase (Cre) of Bacteriophage P1. Generation of different tissue-specific Cre transgenic mice, which can be used for conditional gene inactivation in specific tissues, is an ideal tool for studying gene function in different tissues in mice. The winged-helix transcription factor, Foxa2, is essential for development of the node and notochord. In mouse, Foxa2 expression is observed in the node, notochord, floor plate and gut epithelium during development. In order to facilitate genetic studies of notochord development, we have used a 520 bp element (mNE) upstream of the Foxa2 gene, which directs specific expression in the node and notochord to generate a mouse line, mNE-Cre, in which the Cre gene was placed under the regulatory control of the mNE and linked to an IRES-lacZ reporter. Staining for b-galactocidase (b-gal) activity revealed that the Cre transgene was expressed from E7.5 to E9.5 specifically in the notochord. Moreover, crossing of the mNE-Cre transgenic mice with the loxP mouse reporter line, Z/EG, resulted in enhanced green fluorescent protein (EGFP) signal specifically in the node and notochord from E8.0 to E9.5. The mNE-Cre mice have been used to conditionally inactivate Smoothened (Smo) in the notochord, and preliminary data revealed that loss of both alleles of Smo in the notochord resulted in embryonic lethality. The mNE-Cre transgenic mice are therefore a useful resource for conditional gene manipulation in the notochord in mice.link_to_subscribed_fulltex

T cell shape and function is orchestrated by a network of T polarity proteins

Loss of polarity is one of the earliest hallmarks of epithelial neoplasia and leads to aberrant communication between the epithelial cell and its microenvironment. Understanding how deregulation of polarity occurs and how it may contribute to tumour formation is a new and unexplored area of cancer research. Genetic screens in Drosophila have identified scribble, discs large (dlg) and lethal giant larvae (lgl) as key epithelial polarity regulators with mutation in any of these genes resulting in loss of polarity, overproliferation and multilayering of epithelial cells leading to 3D-tumourous overgrowth, and in the presence of activated Ras, invasion and metastasis. We have recently described the human homologue of Scribble and demonstrated using complementation studies in Drosophila that expression of human Scribble can also regulate polarity and proliferation. Evidence from cancer patients suggests that Scribble and Dlg could act as a tumour suppressor in some epithelial cancers with, in many cases, low levels of Scribble or Dlg correlating with increased tumour invasiveness and malignancy. We have undertaken a detailed functional analysis of Scribble in mammalian epithelial cells and mice mutant for Scribble and uncovered a critical role for Scribble in the regulation of epithelial polarity required for directed migration during development and wound healing in vivo. In addition, we show that impaired human Scribble can function together with activated Ras to lead to increased invasion and tumourigenesis. Therefore, Scribble can act to promote or inhibit migration dependent on the cellular context. We propose that Scribble and other polarity regulators may be key signalling molecules involved in a new pathway regulating epithelial tumour progression in mammals

Imaging of pulmonary hypertension in adults: a position paper from the Fleischner Society

Pulmonary hypertension (PH) is defined by a mean pulmonary artery pressure greater than 20 mm Hg and classified into five different groups sharing similar pathophysiologic mechanisms, hemodynamic characteristics, and therapeutic management. Radiologists play a key role in the multidisciplinary assessment and management of PH. A working group was formed from within the Fleischner Society based on expertise in the imaging and/or management of patients with PH, as well as experience with methodologies of systematic reviews. The working group identified key questions focusing on the utility of CT, MRI, and nuclear medicine in the evaluation of PH: (a) Is noninvasive imaging capable of identifying PH? (b) What is the role of imaging in establishing the cause of PH? (c) How does imaging determine the severity and complications of PH? (d) How should imaging be used to assess chronic thromboembolic PH before treatment? (e) Should imaging be performed after treatment of PH? This systematic review and position paper highlights the key role of imaging in the recognition, work-up, treatment planning, and follow-up of PH