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- Batool, Tahira
(författare)
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Heparan sulfate dependent cell signaling and associated pathophysiology : Implications in tumorigenesis and embryogenesis
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Heparan sulfate proteoglycans (HSPGs) consist of a protein core to which several linear, negatively charged heparan sulfate (HS) chains are covalently attached. HSPGs are expressed on the cell surface and in the extra-cellular matrix (ECM) where they have diverse biological functions, for example co-receptor functions. The diverse functions of HS are linked to structural variability of the polysaccharide. In this thesis, I investigated HS structure-function relationship by using different cell and animal models of one HS-biosynthetic enzyme, glucuronyl C5-epimerase (Hsepi) and one enzyme responsible for post synthetic modification, heparanase.Deletion of Hsepi in mice resulted in neonatal lethality, with multiple organ defects, indicating the importance of HS in embryogenesis. Up-regulated expression of heparanase is found in most human tumor tissues, correlating with increased metastatic potential and decreased survival of cancer patients.In the first project, I focused on the effects of HS on cancer associated cell signaling and found that heparanase overexpression attenuated TGF-β1 stimulated Smad phosphorylation in tumor cells because of increased sulfation degree and turnover rate of HS.Heparanase role in cancer progression has led to clinical trials where inhibition of heparanase activity is currently being evaluated as a potential cancer treatment. Heparin, a HS-related polysaccharide, is being used to inhibit heparanase activity. In my second project, we studied the effect of low molecular weight heparin (LMWH) on cisplatin resistance of ovarian cancer cells (A2780cis). LMWH treatment of A2780cis cells reduced Wnt-activity in these cells and consequently reduce the drug resistance.In paper III, we continued exploring the HS/heparanase role in cancer by using heparanase overexpressing mice (Hpa-tg). We found Lewis Lung Carcinoma (LLC2) cells showed faster growth, bigger tumors and more metastasis in the Hpa-tg mice as compared to wild-type (WT) mice, because of suppressed antitumor immunity in the Hpa-tg mice.In paper IV and V, we studied the structure-function relationship of HS by using Hsepi-/- mice model. Hsepi-/- results in HS-chains lacking IdoA, which makes the chain rigid and consequently affects its co-receptor function. Skeletal malformation in Hsepi-/- mice, led us in paper IV to investigate bone morphogenic protein (BMP), an important signal molecule during embryogenesis and known to interact with HS. We found upregulation of a number of BMPs and expression of P-smad1/5/8, but reduced expression of inhibitory Smads and Gremlin1 in the Hsepi-/- MEF cells. The study indicated that the developmental defects in Hsepi mice could be contributed by a higher BMP signaling. In paper V we investigated the lung of the Hsepi-/- mice. The distal lung of 17.5 days old embryos remained populated by epithelial tubules, because of impaired differentiation of type I cells of the lungs. Potential mechanisms behind the failure of type I cell formation was identified to be reduced vascularization and a sustained signaling of Smad pathways.
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| 2. |
- Hopkins, Sarah, et al.
(författare)
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Mig6 Is a Sensor of EGF Receptor Inactivation that Directly Activates c-Abl to Induce Apoptosis during Epithelial Homeostasis.
- 2012
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Ingår i: Developmental Cell. - : Elsevier BV. - 1534-5807 .- 1878-1551. ; 23:3, s. 547-559
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Tidskriftsartikel (refereegranskat)abstract
- A fundamental aspect of epithelial homeostasis is the dependence on specific growth factors for cell survival, yet the underlying mechanisms remain obscure. We found an "inverse" mode of receptor tyrosine kinase signaling that directly links ErbB receptor inactivation to the induction of apoptosis. Upon ligand deprivation Mig6 dissociates from the ErbB receptor and binds to and activates the tyrosine kinase c-Abl to trigger p73-dependent apoptosis in mammary epithelial cells. Deletion of Errfi1 (encoding Mig6) and inhibition or RNAi silencing of c-Abl causes impaired apoptosis and luminal filling of mammary ducts. Mig6 activates c-Abl by binding to the kinase domain, which is prevented in the presence of epidermal growth factor (EGF) by Src family kinase-mediated phosphorylation on c-Abl-Tyr488. These results reveal a receptor-proximal switch mechanism by which Mig6 actively senses EGF deprivation to directly activate proapoptotic c-Abl. Our findings challenge the common belief that deprivation of growth factors induces apoptosis passively by lack of mitogenic signaling.
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| 3. |
- Linderoth, Emma, et al.
(författare)
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Activated Cdc42-associated Kinase 1 (Ack1) Is Required for Tumor Necrosis Factor-related Apoptosis-inducing Ligand (TRAIL) Receptor Recruitment to Lipid Rafts and Induction of Cell Death
- 2013
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 288:46, s. 32922-32931
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Tidskriftsartikel (refereegranskat)abstract
- TNF-related apoptosis-inducing ligand (TRAIL) holds promise for treatment of cancer due to its ability to selectively kill cancer cells while sparing normal cells. Ligand-induced translocation of TRAIL receptors (TRAIL-R) 1 and 2 (also called DR4 and DR5, respectively) into lipid raft membrane microdomains is required for TRAIL-induced cell death by facilitating receptor clustering and formation of the death-inducing signaling complex, yet the underlying regulatory mechanisms remain largely unknown. We show here that the non-receptor tyrosine kinase Ack1, previously implicated in the spatiotemporal regulation of the EGF receptor, is required for TRAIL-induced cell death in multiple epithelial cell lines. TRAIL triggered a transient up-regulation of Ack1 and its recruitment to lipid rafts along with TRAIL-R1/2. siRNA-mediated depletion of Ack1 disrupted TRAIL-induced accumulation of TRAIL-R1/2 in lipid rafts and efficient recruitment of caspase-8 to the death-inducing signaling complex. Pharmacological inhibition of Ack1 did not affect TRAIL-induced cell death, indicating that Ack1 acts in a kinase-independent manner to promote TRAIL-R1/2 accumulation in lipid rafts. These findings identify Ack1 as an essential player in the spatial regulation of TRAIL-R1/2.
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| 4. |
- Petkova, Milena, et al.
(författare)
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Lymphatic malformations : mechanistic insights and evolving therapeutic frontiers
- 2024
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Ingår i: Journal of Clinical Investigation. - : American Society For Clinical Investigation. - 0021-9738 .- 1558-8238. ; 134:6
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Tidskriftsartikel (refereegranskat)abstract
- The lymphatic vascular system is gaining recognition for its multifaceted role and broad pathological significance. Once perceived as a mere conduit for interstitial fluid and immune cell transport, recent research has unveiled its active involvement in critical physiological processes and common diseases, including inflammation, autoimmune diseases, and atherosclerosis. Consequently, abnormal development or functionality of lymphatic vessels can result in serious health complications. Here, we discuss lymphatic malformations (LMs), which are localized lesions that manifest as fluid -filled cysts or extensive infiltrative lymphatic vessel overgrowth, often associated with debilitating, even life -threatening, consequences. Genetic causes of LMs have been uncovered, and several promising drug -based therapies are currently under investigation and will be discussed.
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| 7. |
- Pilia, Giulia, 1987-
(författare)
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Novel Roles of the Ack1 Kinase in Epithelial Biology
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Epithelial homeostasis is maintained through integration of diverse signals that regulate cell fate. A strict control of such signals is required to prevent overproliferation and, ultimately, oncogenesis. In this thesis we identify novel roles of Activated Cdc42-associated kinase 1 (Ack1) in maintenance of epithelial homeostasis. Ack1 has been previously linked to cytoskeletal remodeling, signal transduction and gene expression regulation. Interestingly, our work reveals that Ack1 is also important for I) promoting extrinsic apoptosis, II) mediating mechanically-induced inhibition of proliferation and III) attenuating mitogenic signals, fundamental functions to prevent aberrant tissue growth.Apoptosis is a program of regulated cell death that can be triggered by several pathways. Among them, the TNF-related apoptosis-inducing ligand (TRAIL)-induced apoptosis cascade has raised interest for cancer treatment, as many cancer cell lines are susceptible to it. We found that Ack1 increases sensitivity to TRAIL by promoting translocation of ligand-bound TRAIL-Receptor to lipid rafts. Localisation at the lipid rafts, in turn, favors recruitment of downstream signalling effectors, enhancing the apoptotic response.Yap and Taz are transcriptional co-factors that integrate mechanical and soluble cues to regulate cell proliferation and differentiation. Yap/Taz regulation is mediated by cytoplasmic sequestration and, particularly for Taz, proteasomal degradation via ubiquitination by the E3 ligase β-TrCP. We discovered that Ack1 is activated by mechanical signals and promotes nuclear exclusion of Yap/Taz. Ack1 promotes Yap/Taz interaction with β-TRCP and it is required for efficient degradation of Taz. Consequently, Ack1 limits Yap/Taz-dependent gene expression and cell proliferation.The ErbB family of receptor tyrosine kinases mediates pro-survival and proliferative signals of crucial importance in development and cancer. Among the ErbB family members, ErbB3 has significant oncogenic properties as it potently activates the PI3K/Akt signaling pathway. We observe that Ack1 depletion increases ErbB3 total levels, but not EGFR and ErbB2, and is required for both basal turnover of ErbB3 and its ligand-induced degradation. Consequently, Ack1 attenuates ErbB3-dependent signalling upon Neuregulin-1β treatment. Additionally, Ack1 reduces ErbB3 gene expression both at steady state and upon stimulation, revealing its importance as multi-level regulator of ErbB3.Taken together, our data depict new roles for Ack1 in epithelial cells, highlighting its multifaceted role in maintenance of epithelial homeostasis.
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