Browsing by Subject "Golgi apparatus"

Now showing 1 - 5 of 5
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    Comparative distribution of carbohydrates and lipid droplets in the Golgi apparatus of intestinal absorptive cells
    (Rockefeller University Press, 1971) Sage, Jean A.; Jersild, Ralph A., Jr.; Anatomy, Cell Biology and Physiology, School of Medicine
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    A Computational Approach for Defining a Signature of β-Cell Golgi Stress in Diabetes
    (American Diabetes Association, 2020-11) Bone, Robert N.; Oyebamiji, Olufunmilola; Talware, Sayali; Selvaraj, Sharmila; Krishnan, Preethi; Syed, Farooq; Wu, Huanmei; Evans-Molina, Carmella; Pediatrics, School of Medicine
    The Golgi apparatus (GA) is an important site of insulin processing and granule maturation, but whether GA organelle dysfunction and GA stress are present in the diabetic β-cell has not been tested. We used an informatics-based approach to develop a transcriptional signature of β-cell GA stress using existing RNA sequencing and microarray data sets generated using human islets from donors with diabetes and islets where type 1 (T1D) and type 2 (T2D) diabetes had been modeled ex vivo. To narrow our results to GA-specific genes, we applied a filter set of 1,030 genes accepted as GA associated. In parallel, we generated an RNA-sequencing data set from human islets treated with brefeldin A (BFA), a known GA stress inducer. Overlapping the T1D and T2D groups with the BFA data set, we identified 120 and 204 differentially expressed genes, respectively. In both the T1D and T2D models, pathway analyses revealed that the top pathways were associated with GA integrity, organization, and trafficking. Quantitative RT-PCR was used to validate a common signature of GA stress that included ATF3, ARF4, CREB3, and COG6 Taken together, these data indicate that GA-associated genes are dysregulated in diabetes and identify putative markers of β-cell GA stress.
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    Effect of ionophores on the processing of theβ-amyloid precursor protein in different cell lines
    (Springer, 1994) Lahiri, Debomoy K.; Medical and Molecular Genetics, School of Medicine
    1. Alzheimer's disease is characterized by the deposition in the brain of extracellular amyloid plaques and vascular deposits consisting mostly of amyloidβ-peptide (Aβ). Aβ, a polypeptide of 39–43 amino acids (M r, ∼4 kDa), is derived proteolytically from a family of proteins of 695–770 amino acids (M r, ∼110–140 kDa) calledβ-amyloid precursor protein (βAPP). 2. βAPP, an integral membrane glycoprotein, is extensively posttranslationally modified within the endoplasmic reticulum (ER) and various Golgi compartments.βAPP is cleaved by proteases in either the trans-Golgi network or the post-Golgi apparatus and then secreted as a truncated soluble form into the conditioned media of cultured cells and cerebrospinal fluid samples from human subjects.βAPP can be processed either by an antiamyloidogenic secretory pathway or by an endosomal/lysosomal pathway. 3. I studied the effect of two ionophores on the processing ofβAPP in cultured cells. Monensin and, in some cases, ammonium chloride increase the intracellular accumulation ofβAPP in several cell lines and may alter its processing. Monensin, which had the most consistent effects, also inhibited secretion ofβAPP in a differentiated (growth factor mediated) cell line. Nigericin, with greater K+ selectivity, was less able to alter the accumulation and possible processing of the protein. 4. These results suggest that the increase in the accumulation of intracellularβAPP observed after treating cells with ionophores has some specificity. The selective effect of these ionophores on the metabolism ofβAPP may provide a model system to analyze the pathways for studying maturation, secretion, and degradation ofβAPP.
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    Mutations in the COPI coatomer subunit α-COP induce release of Aβ-42 and amyloid precursor protein intracellular domain and increase tau oligomerization and release
    (Elsevier, 2021) Astroski, Jacob W.; Akporyoe, Leonora K.; Androphy, Elliot J.; Custer, Sara K.; Dermatology, School of Medicine
    Understanding the cellular processes that lead to Alzheimer's disease (AD) is critical, and one key lies in the genetics of families with histories of AD. Mutations a complex known as COPI were found in families with AD. The COPI complex is involved in protein processing and trafficking. Intriguingly, several recent publications have found components of the COPI complex can affect the metabolism of pathogenic AD proteins. We reduced levels of the COPI subunit α-COP, altering maturation and cleavage of amyloid precursor protein (APP), resulting in decreased release of Aβ-42 and decreased accumulation of the AICD. Depletion of α-COP reduced uptake of proteopathic Tau seeds and reduces intracellular Tau self-association. Expression of AD-associated mutant α-COP altered APP processing, resulting in increased release of Aβ-42 and increased intracellular Tau aggregation and release of Tau oligomers. These results show that COPI coatomer function modulates processing of both APP and Tau, and expression of AD-associated α-COP confers a toxic gain of function, resulting in potentially pathogenic changes in both APP and Tau.
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    Targeting of tail-anchored membrane proteins to subcellular organelles in Toxoplasma gondii
    (Wiley, 2017) Padgett, Leah R.; Arrizabalaga, Gustavo; Sullivan, William J., Jr.; Pharmacology and Toxicology, School of Medicine
    Proper protein localization is essential for critical cellular processes, including vesicle-mediated transport and protein translocation. Tail-anchored (TA) proteins are integrated into organellar membranes via the C-terminus, orienting the N-terminus towards the cytosol. Localization of TA proteins occurs posttranslationally and is governed by the C-terminus, which contains the integral transmembrane domain (TMD) and targeting sequence. Targeting of TA proteins is dependent on the hydrophobicity of the TMD as well as the length and composition of flanking amino acid sequences. We previously identified an unusual homologue of elongator protein, Elp3, in the apicomplexan parasite Toxoplasma gondii as a TA protein targeting the outer mitochondrial membrane. We sought to gain further insight into TA proteins and their targeting mechanisms using this early-branching eukaryote as a model. Our bioinformatics analysis uncovered 59 predicted TA proteins in Toxoplasma, 9 of which were selected for follow-up analyses based on representative features. We identified novel TA proteins that traffic to specific organelles in Toxoplasma, including the parasite endoplasmic reticulum, mitochondrion, and Golgi apparatus. Domain swap experiments elucidated that targeting of TA proteins to these specific organelles was strongly influenced by the TMD sequence, including charge of the flanking C-terminal sequence.