Faculty Bibliography
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Department/Unit:Cell Biology
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14237
A structural perspective on mechanism and function of the cytochrome bc (1) complex
The cytochrome bc (1) complex is a fundamental component of the energy conversion machinery of respiratory and photosynthetic electron transfer chains. The multi-subunit membrane protein complex couples electron transfer from hydroquinone to cytochrome c to the translocation of protons across the membrane, thereby substantially contributing to the proton motive force that is used for ATP synthesis. Considerable progress has been made with structural and functional studies towards complete elucidation of the Q cycle mechanism, which was originally proposed by Mitchell 30 years ago. Yet, open questions regarding key steps of the mechanism still remain. The role of the complex as a major source of reactive oxygen species and its implication in pathophysiological conditions has recently gained interest.
PMID: 18038116
ISSN: 0080-1844
CID: 160519
Using genetically modified microvascular free flaps to deliver local cancer immunotherapy with minimal systemic toxicity
BACKGROUND: Clinical use of cancer gene therapy has been prevented by the inability to deliver high levels of local transgene expression with acceptable host toxicity. The authors' laboratory has developed an ex vivo technique to genetically modify free flaps to deliver immunotherapy locally without systemic toxicity. METHODS: Superficial inferior epigastric flaps were dissected in Fischer rats, perfused with a viral vector expressing the antitumor interleukin-12 (IL-12) for 1 hour, and re-anastomosed. Beneath the flaps was a bolus of 1 x 10(6) beta-human chorionic gonadotropin-secreting MADB-106 tumor cells. Tumor growth was monitored using beta-human chorionic gonadotropin levels (secreted by the tumor) and size. IL-12 expression in tissue was assessed by enzyme-linked immunosorbent assay. Tumor inflammatory infiltrate was assessed using immunohistologic staining (CD8 and CD161) and enzyme-linked immunosorbent assay (interferon-gamma). Serum levels of liver enzymes and histologic analysis were used to assess systemic toxicity. RESULTS: IL-12 expression was confirmed in the flap and surrounding tissue. The rate of tumor growth in the IL-12-treated group was significantly suppressed compared with the control group (p < 0.001). Liver enzyme levels remained normal, and histological evaluation of the liver, lung, and spleen revealed no evidence of inflammation in the treated group. CONCLUSIONS: Using genetically modified free flaps, the authors were able to deliver IL-12 directly into the local environment of a tumor and suppress its growth without eliciting toxic systemic effects. This technique could provide valuable adjuvant treatment after oncologic surgery for soft-tissue cancers, with the transduced flap reconstructing the defect and supplying a therapeutic agent to the resected tumor bed.
PMID: 18453976
ISSN: 1529-4242
CID: 159191
Genetic classification of severe early childhood caries by use of subtracted DNA fragments from Streptococcus mutans
Streptococcus mutans is one of several members of the oral indigenous biota linked with severe early childhood caries (S-ECC). Because most humans harbor S. mutans, but not all manifest disease, it has been proposed that the strains of S. mutans associated with S-ECC are genetically distinct from those found in caries-free (CF) children. The objective of this study was to identify common DNA fragments from S. mutans present in S-ECC but not in CF children. Using suppressive subtractive hybridization, we found a number of DNA fragments (biomarkers) present in 88 to 95% of the S-ECC S. mutans strains but not in CF S. mutans strains. We then applied machine learning techniques including support vector machines and neural networks to identify the biomarkers with the most predictive power for disease status, achieving a 92% accurate classification of the strains as either S-ECC or CF associated. The presence of these gene fragments in 90 to 100% of the 26 S-ECC isolates tested suggested their possible functional role in the pathogenesis of S. mutans associated with dental caries.
PMCID:2546765
PMID: 18596144
ISSN: 0095-1137
CID: 156784
American journal of physiology. Renal physiology. 2008:294(6):F1415-21.DOI: 10.1152/ajprenal.00533.2007
Label-retaining cells of the bladder: candidate urothelial stem cells
Adult tissue stem cells replicate infrequently, retaining DNA nucleotide label (BrdU) for much longer periods than mature, dividing cells in which the label is diluted during a chase period. Those 'label-retaining cells' (LRCs) have been identified as the tissue stem cells in skin, cornea, intestine, and prostate. However, in the urinary tract uroepithelial stem cells have not yet been identified. In this study, BrdU administration identified urothelial LRCs in the rat bladder with 9% of the epithelial basal cells retaining BrdU label 1 yr after its administration. Markers for stem cells in other tissues, Bcl, p63, cytokeratin 14, and beta1 integrin, were immunolocalized in the basal bladder epithelium in or near urothelial LRCs, but not uniquely limited to these cells. Flow cytometry demonstrated that urothelial LRCs were small, had low granularity, and were uniquely beta4 integrin bright. Urothelium from long-term labeled bladders was cultured and LRCs were found to be significantly more clonogenic and proliferative, characteristics of stem cells, than unlabeled urothelial cells. Thus, this work demonstrates that LRCs in the bladder localize to the basal layer, are small, low granularity, uniquely beta4 integrin rich, slowly cycling and demonstrate superior clonogenic and proliferative ability compared with unlabeled epithelial cells. We propose that LRCs represent putative urothelial stem cells
PMID: 18367656
ISSN: 1931-857X
CID: 133040
Marked calpastatin (CAST) depletion in Alzheimer's disease accelerates cytoskeleton disruption and neurodegeneration: neuroprotection by CAST overexpression
Increased activity of calpains is implicated in synaptic dysfunction and neurodegeneration in Alzheimer's disease (AD). The molecular mechanisms responsible for increased calpain activity in AD are not known. Here, we demonstrate that disease progression is propelled by a marked depletion of the endogenous calpain inhibitor, calpastatin (CAST), from AD neurons, which is mediated by caspase-1, caspase-3, and calpains. Initial CAST depletion focally along dendrites coincides topographically with calpain II and ERK 1/2 activation, tau cleavage by caspase-3, and tau and neurofilament hyperphosphorylation. These same changes, together with cytoskeletal proteolysis and neuronal cell death, accompany CAST depletion after intrahippocampal kainic acid administration to mice, and are substantially reduced in mice overexpressing human CAST. Moreover, CAST reduction by shRNA in neuronal cells causes calpain-mediated death at levels of calcium-induced injury that are sublethal to cells normally expressing CAST. Our results strongly support a novel hypothesis that CAST depletion by multiple abnormally activated proteases accelerates calpain dysregulation in AD leading to cytoskeleton disruption and neurodegeneration. CAST mimetics may, therefore, be neuroprotective in AD
PMCID:2819018
PMID: 19020018
ISSN: 1529-2401
CID: 94362
Fibrate therapy: an update
Fibrates are a class of lipid-lowering medication primarily used as second-line agents behind statins. Acting via the peroxisome proliferators-activated receptor-alpha, their main lipoprotein effects are to lower serum triglyceride levels and to raise high-density lipoprotein-cholesterol, with modest effects on low-density lipoprotein-cholesterol. However, many clinical trials indicate that fibrates may have benefits beyond simply altering one's lipid profile. Several angiographic studies show retardation in the progression of atherosclerotic lesions in coronary vessels. Although clinical trials have failed to show a reduction in mortality with fibrates, several post hoc analyses indicate that there may be a mortality benefit in patients with features of the metabolic syndrome. Given that fibrates are often used as second-line agents, it is essential they are safe to be given in combination with other agents, particularly statins and ezetimibe. Although the side-effect profile of fibrates includes gastrointestinal symptoms, increased liver function tests, a reversible rise in creatinine and myositis, in general, fibrates seem to be safe to use in combination with other lipid lowering medications. Thus far, fibrates have not shown a mortality benefit in randomized clinical trials; as a result, they cannot be considered first-line medication for the primary or secondary prevention of coronary artery disease
PMID: 18414184
ISSN: 1538-4683
CID: 79383
Germ cells are forever
Germ cells are the only cell type capable of generating an entirely new organism. In order to execute germline-specific functions and to retain the capacity for totipotency, germ cells repress somatic differentiation, interact with a specialized microenvironment, and use germline-specific networks of RNA regulation
PMID: 18295574
ISSN: 1097-4172
CID: 76157
Human Proteinpedia enables sharing of human protein data [Letter]
PMID: 18259167
ISSN: 1546-1696
CID: 76647
Type III neuregulin-1 promotes oligodendrocyte myelination
The axonal signals that regulate oligodendrocyte myelination during development of the central nervous system (CNS) have not been established. In this study, we have examined the regulation of oligodendrocyte myelination by the type III isoform of neuregulin-1 (NRG1), a neuronal signal essential for Schwann cell differentiation and myelination. In contrast to Schwann cells, primary oligodendrocytes differentiate normally when cocultured with dorsal root ganglia (DRG) neurons deficient in type III NRG1. However, they myelinate type III NRG1-deficient neurites poorly in comparison to wild type cultures. Type III NRG1 is not sufficient to drive oligodendrocyte myelination as sympathetic neurons are not myelinated even with lentiviral-mediated expression of NRG1. Mice haploinsufficient for type III NRG1 are hypomyelinated in the brain, as evidenced by reduced amounts of myelin proteins and lipids and thinner myelin sheaths. In contrast, the optic nerve and spinal cord of heterozygotes are myelinated normally. Together, these results implicate type III NRG1 as a significant determinant of the extent of myelination in the brain and demonstrate important regional differences in the control of CNS myelination. They also indicate that oligodendrocyte myelination, but not differentiation, is promoted by axonal NRG1, underscoring important differences in the control of myelination in the CNS and peripheral nervous system (PNS)
PMID: 18080294
ISSN: 0894-1491
CID: 76859
Inhibition of transforming growth factor betal (TGF beta 1) signaling increases radiosensitivity in breast cancer cell lines [Meeting Abstract]
BIOSIS:PREV200800484702
ISSN: 0197-016x
CID: 104663
