27 research outputs found

    Apical Membrane Antigen 1 (AMA-1): Role in Plasmodium yoelii Infectivity

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    Plasmodium enters the blood stream of a mammalian host via a bite by an infected Anopheles mosquito. Translocation to the liver and introduction into a hepatocyte is a critical step for infectivity of the malaria parasite. Entry of the parasite follows two distinct pathways: rupturing of the hepatocyte membrane by migration or by the adhesion, internalization, and formation of a vacuole within the hepatocyte (Silvie et. al., 2004b). Only the latter pathway is necessary for the differentiation and proliferation of the blood-stage pathogen. My focus will be primarily on the interaction of cell-surface proteins between the hepatocyte and the parasite. There are two well-studied proteins secreted by apical micronemes (i.e. vesicles at the anterior tip of the protozoan which secrete enzymes for parasite entry): the circumsporozoite protein (CSP) and the thrombospodin-related adhesive protein (TRAP; Silvie et. al., 2004b). The exocytosis of CSP and TRAP from micronemes within the parasite is dependent on the transient increase of intracellular calcium. Once the micronemes are excreted, CSP and TRAP localize to the membrane of Plasmodium. This process exposes CSP and TRAP to interact with hepatocyte cell-surface proteins, thus allowing the internalization and infection of the parasite by an unknown mechanism. A parasitophorous vacuole (PV) is formed after internalization, which is required for the differentiation of the exoerythrocytic form (EEF; Silvie et. al., 2004b).... ...Based on evidence seen in HepG2 cells, I will test the efficacy of anti-AMA-1 mAb in mice to neutralize the infectivity of Plasmodium yoelii in primary hepatocyte cultures from wild-type mice. Previously, HepG2 cells were protected against Plasmodium infectivity with increasing concentrations of anti-AMA-1 mAb (Silvie et. al., 2004a). Secondly, I will test the infectivity of P. yoelli on primary hepatocytes from mice preincubated with anti-AMA-1 mAb and treated 3 hours post sporozoite introduction. In the past, HepG2 cells were found susceptible to Plasmodium infection after this procedure (Silvie et. al., 2004a). . This study will further verify the necessity of the AMA-1 protein for sporozoite entry into hepatocytes and subsequent infection

    Life After Lake Forest College: Where are they now?

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    ...Before talking with the alumni, I felt that graduating from college marked a fork in the road of life. I believed that by choosing one path, one would have difficulty back-tracking or switching paths. Upon receiving corresponding with Allison Huang’s ’98, Silvia Skripkauskas’ ’04, Allison Huang ’98, and Brandon Johnson ’01 [four recent biology alumni from Lake Forest College], I realized that changing one’s mind is a natural and sometimes necessary step in life

    Contribution of Alanine-76 and Serine Phosphorylation in α-Synuclein Membrane Association and Aggregation in Yeasts

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    In Parkinson's disease (PD), misfolded and aggregated α-synuclein protein accumulates in degenerating midbrain dopaminergic neurons. The amino acid alanine-76 in α-synuclein and phosphorylation at serine-87 and serine-129 are thought to regulate its aggregation and toxicity. However, their exact contributions to α-synuclein membrane association are less clear. We found that α-synuclein is indeed phosphorylated in fission yeast and budding yeast, the two models that we employed for assessing α-synuclein aggregation and membrane association properties, respectively. Surprisingly, blocking serine phosphorylation (S87A, S129A, and S87A/S129A) or mimicking it (S87D, S129D) altered α-synuclein aggregation in fission yeast. Either blocking or mimicking this phosphorylation increased endomembrane association in fission yeast, but only mimicking it decreased plasma membrane association in budding yeast. Polar substitution mutations of alanine-76 (A76E and A76R) decreased α-synuclein membrane association in budding yeast and decreased aggregation in fission yeast. These yeast studies extend our understanding of serine phosphorylation and alanine-76 contributions to α-synuclein aggregation and are the first to detail their impact on α-synuclein's plasma membrane and endomembrane association

    Activation of Multiple ERBB Family Receptors Mediates Glioblastoma Cancer Stem-like Cell Resistance to EGFR-Targeted Inhibition12

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    Epidermal growth factor receptor (EGFR) signaling is strongly implicated in glioblastoma (GBM) tumorigenesis. However, molecular agents targeting EGFR have demonstrated minimal efficacy in clinical trials, suggesting the existence of GBM resistance mechanisms. GBM cells with stem-like properties (CSCs) are highly efficient at tumor initiation and exhibit therapeutic resistance. In this study, GBMCSC lines showed sphere-forming and tumor initiation capacity after EGF withdrawal from cell culture media, compared with normal neural stem cells that rapidly perished after EGF withdrawal. Compensatory activation of related ERBB family receptors (ERBB2 and ERBB3) was observed in GBM CSCs deprived of EGFR signal (EGF deprivation or cetuximab inhibition), suggesting an intrinsic GBM resistance mechanism for EGFR-targeted therapy. Dual inhibition of EGFR and ERBB2 with lapatinib significantly reduced GBM proliferation in colony formation assays compared to cetuximab-mediated EGFR-specific inhibition. Phosphorylation of downstream ERBB signaling components (AKT, ERK1/2) and GBM CSC proliferation were inhibited by lapatinib. Collectively, these findings show that GBM therapeutic resistance to EGFR inhibitors may be explained by compensatory activation of EGFR-related family members (ERBB2, ERBB3) enabling GBM CSC proliferation, and therefore simultaneous blockade of multiple ERBB family members may be required for more efficacious GBM therapy
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