Browsing by Subject "Cytoskeletal proteins"

Now showing 1 - 5 of 5
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    A Pak1-PP2A-ERM signaling axis mediates F-actin rearrangement and degranulation in mast cells
    (Elsevier, 2013) Staser, Karl; Shew, Matthew A.; Michels, Elizabeth G.; Mwanthi, Muithi M.; Yang, Feng-Chun; Clapp, D. Wade; Park, Su-Jung; Pediatrics, School of Medicine
    Mast cells coordinate allergy and allergic asthma and are crucial cellular targets in therapeutic approaches to inflammatory disease. Allergens cross-link immunoglobulin E bound at high-affinity receptors on the mast cell's surface, causing release of preformed cytoplasmic granules containing inflammatory molecules, including histamine, a principal effector of fatal septic shock. Both p21 activated kinase 1 (Pak1) and protein phosphatase 2A (PP2A) modulate mast cell degranulation, but the molecular mechanisms underpinning these observations and their potential interactions in common or disparate pathways are unknown. In this study, we use genetic and other approaches to show that Pak1's kinase-dependent interaction with PP2A potentiates PP2A's subunit assembly and activation. PP2A then dephosphorylates threonine 567 of Ezrin/Radixin/Moesin (ERM) molecules that have been shown to couple F-actin to the plasma membrane in other cell systems. In our study, the activity of this Pak1-PP2A-ERM axis correlates with impaired systemic histamine release in Pak1(-/-) mice and defective F-actin rearrangement and impaired degranulation in Ezrin disrupted (Mx1Cre(+)Ezrin(flox/flox)) primary mast cells. This heretofore unknown mechanism of mast cell degranulation provides novel therapeutic targets in allergy and asthma and may inform studies of kinase regulation of cytoskeletal dynamics in other cell lineages.
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    A mouse model of BBS identifies developmental and homeostatic effects of BBS5 mutation and identifies novel pituitary abnormalities
    (Oxford University Press, 2021) Bentley-Ford, Melissa R.; Engle, Staci E.; Clearman, Kelsey R.; Haycraft, Courtney J.; Andersen, Reagan S.; Croyle, Mandy J.; Rains, Addison B.; Berbari, Nicolas F.; Yoder, Bradley K.; Biology, School of Science
    Primary cilia are critical sensory and signaling compartments present on most mammalian cell types. These specialized structures require a unique signaling protein composition relative to the rest of the cell to carry out their functions. Defects in ciliary structure and signaling result in a broad group of disorders collectively known as ciliopathies. One ciliopathy, Bardet-Biedl syndrome (BBS; OMIM 209900), presents with diverse clinical features, many of which are attributed to defects in ciliary signaling during both embryonic development and postnatal life. For example, patients exhibit obesity, polydactyly, hypogonadism, developmental delay and skeletal abnormalities along with sensory and cognitive deficits, but for many of these phenotypes it is uncertain, which are developmental in origin. A subset of BBS proteins assembles into the core BBSome complex, which is responsible for mediating transport of membrane proteins into and out of the cilium, establishing it as a sensory and signaling hub. Here, we describe two new mouse models for BBS resulting from a targeted LacZ gene trap allele (Bbs5-/-) that is a predicted congenital null mutation and conditional (Bbs5flox/flox) allele of Bbs5. Bbs5-/- mice develop a complex phenotype consisting of increased pre-weaning lethality craniofacial and skeletal defects, ventriculomegaly, infertility and pituitary anomalies. Utilizing the conditional allele, we show that the male fertility defects, ventriculomegaly and pituitary abnormalities are only present when Bbs5 is disrupted prior to postnatal day 7, indicating a developmental origin. In contrast, mutation of Bbs5 results in obesity, independent of the age of Bbs5 loss.
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    NAHR-mediated copy-number variants in a clinical population: Mechanistic insights into both genomic disorders and Mendelizing traits
    (Cold Spring Harbor Laboratory, 2013) Dittwald, Piotr; Gambin, Tomasz; Szafranski, Przemyslaw; Li, Jian; Amato, Stephen; Divon, Michael Y.; Rodríguez Rojas, Lisa Ximena; Elton, Lindsay E.; Scott, Daryl A.; Schaaf, Christian P.; Torres-Martinez, Wilfredo; Stevens, Abby K.; Rosenfeld, Jill A.; Agadi, Satish; Francis, David; Kang, Sung-Hae L.; Breman, Amy; Lalani, Seema R.; Bacino, Carlos A.; Bi, Weimin; Milosavljevic, Aleksandar; Beaudet, Arthur L.; Patel, Ankita; Shaw, Chad A.; Lupski, James R.; Gambin, Anna; Cheung, Sau Wai; Stankiewicz, Pawel; Medical and Molecular Genetics, School of Medicine
    We delineated and analyzed directly oriented paralogous low-copy repeats (DP-LCRs) in the most recent version of the human haploid reference genome. The computationally defined DP-LCRs were cross-referenced with our chromosomal microarray analysis (CMA) database of 25,144 patients subjected to genome-wide assays. This computationally guided approach to the empirically derived large data set allowed us to investigate genomic rearrangement relative frequencies and identify new loci for recurrent nonallelic homologous recombination (NAHR)-mediated copy-number variants (CNVs). The most commonly observed recurrent CNVs were NPHP1 duplications (233), CHRNA7 duplications (175), and 22q11.21 deletions (DiGeorge/velocardiofacial syndrome, 166). In the ∼25% of CMA cases for which parental studies were available, we identified 190 de novo recurrent CNVs. In this group, the most frequently observed events were deletions of 22q11.21 (48), 16p11.2 (autism, 34), and 7q11.23 (Williams-Beuren syndrome, 11). Several features of DP-LCRs, including length, distance between NAHR substrate elements, DNA sequence identity (fraction matching), GC content, and concentration of the homologous recombination (HR) hot spot motif 5'-CCNCCNTNNCCNC-3', correlate with the frequencies of the recurrent CNVs events. Four novel adjacent DP-LCR-flanked and NAHR-prone regions, involving 2q12.2q13, were elucidated in association with novel genomic disorders. Our study quantitates genome architectural features responsible for NAHR-mediated genomic instability and further elucidates the role of NAHR in human disease.
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    Necroptosis is SARMful to your health
    (Rockefeller University Press, 2020-08-03) Pierchala, Brian A.; Anatomy and Cell Biology, School of Medicine
    Necroptosis is a cell death pathway involved in inflammation and disease. In this issue, Ko et al. (2020. J. Cell Biol.https://doi.org/10.1083/jcb.201912047) link SARM1, the executioner of Wallerian degeneration of axons, to necroptosis, revealing a unique form of axonal disassembly likely involved in neurodegenerative disorders.
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    PAK1's regulation of eosinophil migration and implications for asthmatic inflammation
    (2013-12-19) Mwanthi, Muithi; Clapp, D. Wade; Blum, Janice Sherry, 1957-; Gunst, Susan J.; Wilkes, David S.; Yang, Feng-Chun
    More than 300 million people world-wide suffer from breathlessness, wheezing, chest tightness, and coughing characteristic of chronic bronchial asthma, the global incidence of which is on the rise. Allergen-sensitization and challenge elicits pulmonary expression of chemoattractants that promote a chronic eosinophil-rich infiltrate. Eosinophils are increasingly recognized as important myeloid effectors in chronic inflammation characteristic of asthma, although few eosinophil molecular signaling pathways have successfully been targeted in asthma therapy. p21 activated kinases (PAKs), members of the Ste-20 family of serine/threonine kinases, act as molecular switches in cytoskeletal-dependent processes involved in cellular motility. We hypothesized that PAK1 modulated eosinophil infiltration in an allergic airway disease (AAD) murine model. In this model, Pak1 deficient mice developed reduced inflammatory AAD responses in vivo with notable decreases in eosinophil infiltration in the lungs and broncho-alveolar lavage fluids (BALF). To test the importance of PAK1 in hematopoietic cells in AAD we used complementary bone marrow transplant experiments that demonstrated decreased eosinophil inflammation in hosts transplanted with Pak1 deficient bone marrow. In in vitro studies, we show that eotaxin-signaling through PAK1 facilitated eotaxin-mediated eosinophil migration. Ablating PAK1 expression by genetic deletion in hematopoietic progenitors or siRNA treatment in derived human eosinophils impaired eotaxin-mediated eosinophil migration, while ectopic PAK1 expression promoted this migration. Together these data suggest a key role for PAK1 in the development of atopic eosinophil inflammation and eotaxin-mediated eosinophil migration.