Mechanochemical control of epidermal stem cell divisions by B-plexins

The precise spatiotemporal control of cell proliferation is key to the morphogenesis of epithelial tissues. Epithelial cell divisions lead to tissue crowding and local changes in force distribution, which in turn suppress the rate of cell divisions. However, the molecular mechanisms underlying this mechanical feedback are largely unclear. Here, we identify a critical requirement of B-plexin transmembrane receptors in the response to crowding-induced mechanical forces during embryonic skin development. Epidermal stem cells lacking B-plexins fail to sense mechanical compression, resulting in disinhibition of the transcriptional coactivator YAP, hyperproliferation, and tissue overgrowth. Mechanistically, we show that B-plexins mediate mechanoresponses to crowding through stabilization of adhesive cell junctions and lowering of cortical stiffness. Finally, we provide evidence that the B-plexin-dependent mechanochemical feedback is also pathophysiologically relevant to limit tumor growth in basal cell carcinoma, the most common type of skin cancer. Our data define a central role of B-plexins in mechanosensation to couple cell density and cell division in development and disease.Peer reviewe

Rola terapii przezcewnikowych w leczeniu ostrej zatorowości płucnej — opinia Polskiej Inicjatywy PERT, Sekcji Krążenia Płucnego, Asocjacji Interwencji Sercowo-Naczyniowych i Asocjacji Intensywnej Terapii Kardiologicznej Polskiego Towarzystwa Kardiologicznego

Dzięki postępom w zakresie technologii kardiologii interwencyjnej leczenie przezcewnikowe stało się w ostatnich latach realną opcją terapeutyczną w leczeniu pacjentów z ostrą zatorowością płucną z wysokim ryzykiem wczesnej śmiertelności. Obecnie stosowane techniki przezcewnikowe umożliwiają miejscową fibrynolizę lub embolektomię przy minimalnym ryzyku powikłań. Stąd mogą być rozważane u pacjentów z grupy wysokiego ryzyka jako alternatywa dla chirurgicznej embolektomii płucnej, gdy systemowa tromboliza jest przeciwwskazana lub nieskuteczna. Rozważane są również u pacjentów z grupy średniego–wysokiego ryzyka, u których pomimo leczenia przeciwzakrzepowego nie uzyskano poprawy lub nastąpiło pogorszenie stanu klinicznego. Celem artykułu było przedstawienie roli technik przezcewnikowych w leczeniu chorych z ostrą zatorowością płucną zgodnie z aktualną wiedzą i opinią ekspertów. Leczenie interwencyjne opisano w szerszym kontekście organizacji opieki nad pacjentem. Przedstawiono organizację i zadania zespołu szybkiego reagowania w zatorowości płucnej, rolę obrazowania przedzabiegowego, zasady antykoagulacji okołozabiegowej, kryteria kwalifikacji pacjentów, wyboru odpowiedniego czasu interwencji oraz rolę intensywnej terapii. Szczegółowo omówiono dostępne terapie przezcewnikowe, w tym wystandaryzowane protokoły, definicje sukcesu i niepowodzenia procedury. Niniejszy dokument został opracowany we współpracy z ekspertami z różnych polskich towarzystw naukowych, co podkreśla rolę pracy zespołowej w opiece nad chorym z ostrą zatorowością płucną

Role of catheter-directed therapies in the treatment of acute pulmonary embolism. Expert opinion of the Polish PERT Initiative, Working Group on Pulmonary Circulation, Association of Cardiovascular Interventions, and Association of Intensive Cardiac Care

Thanks to advances in interventional cardiology technologies the catheter-directed treatment has become recently a viable therapeutic option in the treatment of patients with acute pulmonary embolism at high risk of early mortality. Current transcatheter techniques allow local fibrinolysis or embolectomy with minimal risk of complications. Therefore they can be considered in high risk patients as an alternative to surgical pulmonary embolectomy when systemic thrombolysis is contraindicated or ineffective. They are also considered in patients with intermediate — high risk with a lack of improvement or clinical deterioration despite anticoagulation. The purpose of this article is to present the role of transcatheter techniques in the treatment of patients with acute pulmonary embolism. We describe current knowledge and experts’ opinion in this field. Interventional treatment is described in the broader context of patient care organization and therapeutic modalities. We present the organization and responsibilities of pulmonary embolism response teams, the role of pre-procedural imaging, peri-procedural anticoagulation, patients selection, timing of intervention and intensive care support. Currently available catheter directed therapies are discussed in detail including standardized protocols, definitions of procedure success and failure. This expert opinion has been developed in collaboration with experts from various Polish scientific societies signifying the role of teamwork in the care for patients with acute pulmonary embolism

PDZ domains - common players in the cell signaling.

PDZ domains are ubiquitous protein interaction modules that play a key role in cellular signaling. Their binding specificity involves recognition of the carboxyl-terminus of various proteins, often belonging to receptor and ion channel families. PDZ domains also mediate more complicated molecular networks through PDZ-PDZ interactions, recognition of internal protein sequences or phosphatidylinositol moieties. The domains often form a tandem of multiple copies, but equally often such tandems or single PDZ domain occur in combination with other signaling domains (for example SH3, DH/PH, GUK, LIM, CaMK). Common occurrence of PDZ domains in Metazoans strongly suggests that their evolutionary appearance results from the complication of signaling mechanisms in multicellular organisms. Here, we focus on their structure, specificity and role in signaling pathways

Novel peptide recognized by RhoA GTPase

A phage-displayed random 7-mer disulfide bridge-constrained peptide library was used to map the surface of the RhoA GTPase and to find peptides able to recognize RhoA switch regions. Several peptide sequences were selected after four rounds of enrichment, giving a high signal in ELISA against RhoA-GDP. A detailed analysis of one such selected peptide, called R2 (CWSFPGYAC), is reported. The RhoA - R2 interaction was investigated using fluorescence spectroscopy, chemical denaturation, and determination of the kinetics of nucleotide exchange and GTP hydrolysis in the presence of RhoA regulatory proteins. All measurements indicate that the affinity of the R2 peptide for RhoA is in the micromolar range and that R2 behaves as an inhibitor of: i) GDP binding to the apo form of RhoA (Mg2+- and nucleotide-free form of the GTPase), ii) nucleotide exchange stimulated by GEF (DH/PH tandem from PDZRhoGEF), and iii) GTP hydrolysis stimulated by the BH domain of GrafGAP protein

Finding a fitting shoe for Cinderella: Searching for an autophagy inhibitor

Vps34 is the ancestral phosphatidylinositol 3-kinase (PtdIns3K) isoform and is essential for endosomal trafficking of proteins to the vacuole/lysosome, autophagy and phagocytosis. Vps34-containing complexes associate with specific cellular compartments to produce PtdIns(3)P. Understanding the roles of Vps34 has been hampered by the lack of potent, specific inhibitors. To boost development of Vps34 inhibitors, we determined the crystal structures of Vps34 alone and in complexes with multitargeted PtdIns3K inhibitors. These structures provided a first glimpse into the uniquely constricted ATP-binding site of Vps34 and enabled us to model Vps34 regulation. We showed that the substrate-binding “activation” loop and the flexibly attached amphipathic C-terminal helix are crucial for catalysis on membranes. The C-terminal helix also suppresses ATP hydrolysis in the absence of membranes. We propose that membrane binding shifts the C-terminal helix to orient the enzyme for catalysis, and the Vps15 regulatory subunit, which binds to this and the preceding helix, may facilitate this process. This C-terminal region may also represent a target for specific, non-ATP-competitive PtdIns3K inhibitors

Allosteric inhibition of Aurora-A kinase by a synthetic vNAR domain

The vast majority of clinically approved protein kinase inhibitors target the ATP-binding pocket directly. Consequently, many inhibitors have broad selectivity profiles and most have significant off-target effects. Allosteric inhibitors are generally more selective, but are difficult to identify because allosteric binding sites are often unknown or poorly characterized. Aurora-A is activated through binding of TPX2 to an allosteric site on the kinase catalytic domain, and this knowledge could be exploited to generate an inhibitor. Here, we generated an allosteric inhibitor of Aurora-A kinase based on a synthetic, vNAR single domain scaffold, vNAR-D01. Biochemical studies and a crystal structure of the Aurora-A/vNAR-D01 complex show that the vNAR domain overlaps with the TPX2 binding site. In contrast with the binding of TPX2, which stabilizes an active conformation of the kinase, binding of the vNAR domain stabilizes an inactive conformation, in which the αC-helix is distorted, the canonical Lys-Glu salt bridge is broken and the regulatory (R-) spine is disrupted by an additional hydrophobic side chain from the activation loop. These studies illustrate how single domain antibodies can be used to characterize the regulatory mechanisms of kinases and provide a rational basis for structure-guided design of allosteric Aurora-A kinase inhibitors

Rab11‐FIP3 Is Critical for the Structural Integrity of the Endosomal Recycling Compartment

Rab11‐FIP3 is an endosomal recycling compartment (ERC) protein that is implicated in the process of membrane delivery from the ERC to sites of membrane insertion during cell division. Here we report that Rab11‐FIP3 is critical for the structural integrity of the ERC during interphase. We demonstrate that knockdown of Rab11‐FIP3 and expression of a mutant of Rab11‐FIP3 that is Rab11‐binding deficient cause loss of all ERC‐marker protein staining from the pericentrosomal region of A431 cells. Furthermore, we find that fluorophore‐labelled transferrin cannot access the pericentrosomal region of cells in which Rab11‐FIP3 function has been perturbed. We find that this Rab11‐FIP3 function appears to be specific because expression of the equivalent Rab11‐binding deficient mutant of Rab‐coupling protein does not perturb ERC morphology. In addition, we find that other organelles such as sorting and late endosomes are unaffected by loss of Rab11‐FIP3 function. Finally, we demonstrate the presence of an extensive coiled‐coil region between residues 463 and 692 of Rab11‐FIP3, which exists as a dimer in solution and is critical to support its function on the ERC. Together, these data indicate that Rab11‐FIP3 is necessary for the structural integrity of the pericentrosomal ERC

High affinity binders to EphA2 isolated from Abdurin Scaffold libraries; Characterization, binding and tumor targeting

No grant i