Browsing by Subject "Endosomes"

Now showing 1 - 3 of 3
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    Autophagy induced by calcium phosphate precipitates targets damaged endosomes
    (ASBMB, 2014-04-18) Chen, Xi; Khambu, Bilon; Zhang, Hao; Gao, Wentao; Li, Min; Chen, Xiaoyun; Yoshimori, Tamotsu; Yin, Xiao-Ming; Department of Pathology & Laboratory Medicine, IU School of Medicine
    Calcium phosphate precipitates (CPPs) form complexes with DNA, which enter cells via endocytosis. Under this condition CPPs induce autophagy via the canonic autophagy machinery. Here we showed that CPP-induced autophagy was also dependent on endocytosis as the process was significantly inhibited by methyl-β-cyclodextrin and dynasore, which suppress clathrin-dependent endocytosis. Consistently, CPP treatment triggered the formation of filipin-positive intracellular vesicles whose membranes are rich in cholesterol. Unexpectedly, these vesicles were also positive for galectin 3, suggesting that they were damaged and the membrane glycans became accessible to galectins to bind. Endosome damage was caused by endocytosis of CPPs and was reversed by calcium chelators or by endocytosis inhibitors. Notably, CPP-induced LC3-positive autophagosomes were colocalized with galectin 3, ubiquitin, and p62/SQSTM1. Inhibition of galectin 3 reduced p62 puncta and autophagosome formation. Knockdown of p62 additionally inhibited the colocalization of autophagosomes with galectins. Furthermore, most of the galectin 3-positive vesicles were colocalized with Rab7 or LAMP1. Agents that affect endosome/lysosome maturation and function, such as bafilomycin A1, also significantly affected CPP-induced tubulovesicular autophagosome formation. These findings thus indicate that endocytosed CPPs caused endosome damage and recruitment of galectins, particularly at the later endosome stage, which led to the interaction of the autophagosomal membranes with the damaged endosome in the presence of p62.
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    Dynamic regulation of the subunit composition of BK channels in smooth muscle
    (American Heart Association, 2017-09-01) Dick, Gregory M.; Tune, Johnathan D.; Cellular and Integrative Physiology, School of Medicine
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    Precise targeting of POLR2A as a therapeutic strategy for human triple negative breast cancer
    (Springer Nature, 2019-04) Xu, Jiangsheng; Liu, Yunhua; Li, Yujing; Wang, Hai; Stewart, Samantha; Van der Jeught, Kevin; Agarwal, Pranay; Zhang, Yuntian; Liu, Sheng; Zhao, Gang; Wan, Jun; Lu, Xiongbin; He, Xiaoming; Medical and Molecular Genetics, School of Medicine
    TP53 is the most frequently mutated or deleted gene in triple negative breast cancer (TNBC). Both the loss of TP53 and the lack of targeted therapy are significantly correlated with poor clinical outcomes, making TNBC the only type of breast cancer that has no approved targeted therapies. Through in silico analysis, we identified POLR2A in the TP53-neighbouring region as a collateral vulnerability target in TNBC tumours, suggesting that its inhibition via small interfering RNA (siRNA) may be an amenable approach for TNBC targeted treatment. To enhance bioavailability and improve endo/lysosomal escape of siRNA, we designed pH-activated nanoparticles for augmented cytosolic delivery of POLR2A siRNA (siPol2). Suppression of POLR2A expression with the siPol2-laden nanoparticles leads to enhanced growth reduction of tumours characterized by hemizygous POLR2A loss. These results demonstrate the potential of the pH-responsive nanoparticle and the precise POLR2A targeted therapy in TNBC harbouring the common TP53 genomic alteration.