Faculty Bibliography
Searched for:
school:SOM
Department/Unit:Cell Biology
Total Results:
14086
Reduced heterogeneous expression of Cx43 results in decreased Nav1.5 expression and reduced sodium current that accounts for arrhythmia vulnerability in conditional Cx43 knockout mice
BACKGROUND: Reduced expression of connexin 43 (Cx43) and sodium channel (Nav1.5) and increased expression of collagen (fibrosis) are important determinants of impulse conduction in the heart. OBJECTIVE: To study the importance and interaction of these factors at very low Cx43 expression, inducible Cx43 knockout mice with and without inducible ventricular tachycardia (VT) were compared through electrophysiology and immunohistochemistry. METHODS: Cx43(CreER(T)/fl) mice were induced with tamoxifen and killed after 2 weeks. Epicardial activation mapping was performed on Langendorff-perfused hearts, and arrhythmia vulnerability was tested. Mice were divided into arrhythmogenic (VT+; n = 13) and nonarrhythmogenic (VT-; n = 10) animals, and heart tissue was analyzed for Cx43, Nav1.5, and fibrosis. RESULTS: VT+ mice had decreased Cx43 expression with increased global, but not local, heterogeneity of Cx43 than did VT- mice. Nav1.5-immunoreactive protein expression was lower in VT+ than in VT- mice, specifically at sites devoid of Cx43. Levels of fibrosis were similar between VT- and VT+ mice. QRS duration was increased and epicardial activation was more dispersed in VT+ mice than in VT- mice. The effective refractory period was similar between the 2 groups. Premature stimulation resulted in a more severe conduction slowing in VT+ than in VT- hearts in the right ventricle. Separate patch-clamp experiments in isolated rat ventricular myocytes confirmed that the loss of Cx43 expression correlated with the decreased sodium current amplitude. CONCLUSIONS: Global heterogeneity in Cx43 expression and concomitant heterogeneous downregulation of sodium-channel protein expression and sodium current leads to slowed and dispersed conduction, which sensitizes the heart for ventricular arrhythmias
PMCID:3336370
PMID: 22100711
ISSN: 1556-3871
CID: 149999
MAL facilitates the incorporation of exocytic uroplakin-delivering vesicles into the apical membrane of urothelial umbrella cells
The apical surface of mammalian bladder urothelium is covered by large (500-1000 nm) two-dimensional (2D) crystals of hexagonally packed 16-nm uroplakin particles (urothelial plaques), which play a role in permeability barrier function and uropathogenic bacterial binding. How the uroplakin proteins are delivered to the luminal surface is unknown. We show here that myelin-and-lymphocyte protein (MAL), a 17-kDa tetraspan protein suggested to be important for the apical sorting of membrane proteins, is coexpressed with uroplakins in differentiated urothelial cell layers. MAL depletion in Madin-Darby canine kidney cells did not affect, however, the apical sorting of uroplakins, but it decreased the rate by which uroplakins were inserted into the apical surface. Moreover, MAL knockout in vivo led to the accumulation of fusiform vesicles in mouse urothelial superficial umbrella cells, whereas MAL transgenic overexpression in vivo led to enhanced exocytosis and compensatory endocytosis, resulting in the accumulation of the uroplakin-degrading multivesicular bodies. Finally, although MAL and uroplakins cofloat in detergent-resistant raft fractions, they are associated with distinct plaque and hinge membrane subdomains, respectively. These data suggest a model in which 1) MAL does not play a role in the apical sorting of uroplakins; 2) the propensity of uroplakins to polymerize forming 16-nm particles and later large 2D crystals that behave as detergent-resistant (giant) rafts may drive their apical targeting; 3) the exclusion of MAL from the expanding 2D crystals of uroplakins explains the selective association of MAL with the hinge areas in the uroplakin-delivering fusiform vesicles, as well as at the apical surface; and 4) the hinge-associated MAL may play a role in facilitating the incorporation of the exocytic uroplakin vesicles into the corresponding hinge areas of the urothelial apical surface.
PMCID:3315800
PMID: 22323295
ISSN: 1059-1524
CID: 165440
Lack of ceruloplasmin expression alters aspects of copper transport to the fetus and newborn, as determined in mice
Copper transport and accumulation were studied in virgin and lactating C57BL/6 mice, with and without expression of ceruloplasmin (Cp), to assess the importance of Cp to these processes. One hour after i.p. injection of tracer (64)Cu, liver and kidney accounted for 80% of the radioactivity, and mammary gland 1%, while in lactating Cp+/+ mice 2-4 days post partum, uptake by mammary gland was 9-fold higher and that of liver and other organs was decreased, with (64)Cu rapidly appearing in milk. Parallel studies in Cp-/- mice (siblings from same colony) gave virtually identical results. However, their milk contained less (64)Cu, and actual copper contents determined by furnace atomic absorption were less than half those for milk from normal dams. Liver copper concentrations of pups born to Cp-/- dams also were half those of pups from wild type dams. Copper in pup brains was unaffected; but iron concentrations were reduced. We conclude that absence of Cp, while not affecting entry of exchangeable copper from the blood into the mammary gland, does have a significant effect on the availability of this metal to the newborn through the milk and in the form of stores accumulating in gestation.
PMID: 22080201
ISSN: 0966-0844
CID: 281172
Broadly neutralizing antibodies against influenza virus and prospects for universal therapies
Vaccines are the gold standard for the control and prevention of infectious diseases, but a number of important human diseases remain challenging targets for vaccine development. An influenza vaccine that confers broad spectrum, long-term protection remains elusive. Several broadly neutralizing antibodies have been identified that protect against multiple subtypes of influenza A viruses, and crystal structures of several neutralizing antibodies in complex with the major influenza surface antigen, hemagglutinin, have revealed at least 3 highly conserved epitopes. Our understanding of the molecular details of these antibody-antigen interactions has suggested new strategies for the rational design of improved influenza vaccines, and has inspired the development of new antivirals for the treatment of influenza infections.
PMCID:3368890
PMID: 22482710
ISSN: 1879-6265
CID: 2291412
MicroRNAs regulating lipid metabolism in atherogenesis
MicroRNAs have emerged as important post-transcriptional regulators of lipid metabolism, and represent a new class of targets for therapeutic intervention. Recently, microRNA-33a and b (miR-33a/b) were discovered as key regulators of metabolic programs including cholesterol and fatty acid homeostasis. These intronic microRNAs are embedded in the sterol response element binding protein genes, SREBF2 and SREBF1, which code for transcription factors that coordinate cholesterol and fatty acid synthesis. By repressing a variety of genes involved in cholesterol export and fatty acid oxidation, including ABCA1, CROT, CPT1, HADHB and PRKAA1, miR-33a/b act in concert with their host genes to boost cellular sterol levels. Recent work in animal models has shown that inhibition of these small non-coding RNAs has potent effects on lipoprotein metabolism, including increasing plasma high-density lipoprotein (HDL) and reducing very low density lipoprotein (VLDL) triglycerides. Furthermore, other microRNAs are being discovered that also target the ABCA1 pathway, including miR-758, suggesting that miRNAs may work cooperatively to regulate this pathway. These exciting findings support the development of microRNA antagonists as potential therapeutics for the treatment of dyslipidaemia, atherosclerosis and related metabolic diseases.
PMCID:3618663
PMID: 22274626
ISSN: 0340-6245
CID: 166813
Is losartan the drug for all seasons?
PMID: 22445547
ISSN: 1471-4892
CID: 169635
Molecular insights into the heterogeneity of telomere reprogramming in induced pluripotent stem cells
Rejuvenation of telomeres with various lengths has been found in induced pluripotent stem cells (iPSCs). Mechanisms of telomere length regulation during induction and proliferation of iPSCs remain elusive. We show that telomere dynamics are variable in mouse iPSCs during reprogramming and passage, and suggest that these differences likely result from multiple potential factors, including the telomerase machinery, telomerase-independent mechanisms and clonal influences including reexpression of exogenous reprogramming factors. Using a genetic model of telomerase-deficient (Terc(-/-) and Terc(+/-)) cells for derivation and passages of iPSCs, we found that telomerase plays a critical role in reprogramming and self-renewal of iPSCs. Further, telomerase maintenance of telomeres is necessary for induction of true pluripotency while the alternative pathway of elongation and maintenance by recombination is also required, but not sufficient. Together, several aspects of telomere biology may account for the variable telomere dynamics in iPSCs. Notably, the mechanisms employed to maintain telomeres during iPSC reprogramming are very similar to those of embryonic stem cells. These findings may also relate to the cloning field where these mechanisms could be responsible for telomere heterogeneity after nuclear reprogramming by somatic cell nuclear transfer.
PMCID:3317559
PMID: 22184006
ISSN: 1001-0602
CID: 166038
A comparison of the natriuretic and kaliuretic effects of cicletanine and hydrochlorothiazide in prehypertensive and hypertensive humans
OBJECTIVES: The aim of this study was to compare the single-dose effects of thiazide-type diuretics cicletanine and hydrochlorothiazide (HCTZ), on natriuresis and kaliuresis in prehypertensive and treatment-naive, stage 1 hypertensive patients and to explore the impact of GRK4 gene polymorphisms on thiazide-induced urinary electrolyte excretion. METHODS: The study was a randomized, double-blind, placebo-controlled, three-period, four-treatment, balanced incomplete block, cross-over study in male patients assigned to treatment sequences consisting of placebo, cicletanine 50 mg, cicletanine 150 mg, and HCTZ 25 mg, doses used to treat hypertension. Cumulative urine samples were collected predosing and over 24 h after dosing in each period to compare urine electrolyte excretion profiles of potassium (UKV), sodium (UNaV), magnesium, calcium, phosphate, chloride, and pH among groups. Each treatment was administered to 18 different patients in each period, and an equal number of patients had less than and at least three GRK4 allele variants. RESULTS: Compared with placebo, mean UKV was significantly increased with HCTZ 25 mg (12.7 mmol/day; P
PMID: 22278145
ISSN: 1473-5598
CID: 991312
Apoprotein B: quality control early and late in the secretory pathway for this atherogenic protein [Meeting Abstract]
Apoprotein B (apoB100) is required for the formation of VLDL, the precursor of LDL, the plasma level of which is a strong risk factor for atherosclerosis and coronary artery disease (CAD). It is an exceptionally large (>4000 aa) and hydrophobic protein. As the nascent polypeptide is translocating across the ER, if lipids are not transferred to stabilize its conformation, we and others have shown that like other abnormally folded proteins in the ER, its quality control is governed by ER-associated ub-proteasome degradation (ERAD). Using a combination of systems from yeast to genetically modified mice, we and our collaborators have shown apoB100 ERAD to involve chaperone and chaperone-like molecules, such as Hsp70, 90, 110, and p58. The full assembly of VLDL does not occur until the Golgi. We have discovered that nascent particles ("pre-VLDL") that do not complete this maturation process (e.g., under the influence of certain dietary fatty acids), are subject to a late stage quality control process mediated by autophagy. In summary, the production of apoB100-lipoproteins, whose plasma levels correlate with the risk of CAD, is determined in part by quality control processes that recognize features of the protein specific to its stage of assembly and that are separated between the ER and Golgi compartments
EMBASE:70852949
ISSN: 0892-6638
CID: 178107
Guidelines for the use and interpretation of assays for monitoring autophagy [Guideline]
In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
PMCID:3404883
PMID: 22966490
ISSN: 1554-8627
CID: 181862
