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Affiliation(s)
- Mitsuo Yamauchi
- Dental Research Center, University of North Carolina, Chapel Hill, NC, USA
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2
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Ding LH, Shingyoji M, Chen F, Chatterjee A, Kasai KE, Chen DJ. Gene expression changes in normal human skin fibroblasts induced by HZE-particle radiation. Radiat Res 2005; 164:523-6. [PMID: 16187761 DOI: 10.1667/rr3350.1] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Studies have shown that radiation exposure affects global gene expression in mammalian cells. However, little is known about the effects of HZE particles on gene expression. To study these effects, human skin fibroblasts were irradiated with HZE particles of different energies and LETs. The data obtained from these experiments indicate that changes in gene expression are dependent on the energy of the radiation source. Particles with the highest energy, i.e. iron, induced the biggest expression changes in terms of numbers of genes and magnitudes of changes. Many genes were found to undergo significant expression changes after HZE-particle irradiation, including CDKN1A/p21, MDM2, TNFRSF6/fas, PCNA and RAD52. Unlike X rays, HZE particles expose cells to two types of radiation: primary ions and delta rays. We hypothesized that the biological effects of delta rays, which are secondary electron emissions, should resemble the effects of X rays. To explore this idea, gene expression changes between cells that had been irradiated with HZE particles and X rays were compared. The results support our hypothesis since the number of genes that commonly changed after exposure to both radiations increased as a function of particle energy.
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Affiliation(s)
- Liang-Hao Ding
- Lawrence Berkeley National Laboratory, Life Sciences Division, MS74R0157, Berkeley, California 94720, USA
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3
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Batra NN, Li YJ, Yellowley CE, You L, Malone AM, Kim CH, Jacobs CR. Effects of short-term recovery periods on fluid-induced signaling in osteoblastic cells. J Biomech 2005; 38:1909-17. [PMID: 16023480 DOI: 10.1016/j.jbiomech.2004.08.009] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/04/2004] [Indexed: 11/21/2022]
Abstract
It is well known that cyclic mechanical loading can produce an anabolic response in bone. In vivo studies have shown that the insertion of short-term recovery periods (10-15 s) into mechanical loading profiles led to an increased osteogenic response compared to continuous cyclic loading of bone. Although this is suggestive of temporal processing at the bone cell level, there is little evidence to support such a hypothesis. Therefore, the current study investigated the cellular mechanism of bone's response to rest inserted vs. continuous mechanical loading. Cell responses to rest inserted mechanical loading were quantified by applying oscillatory fluid flow (OFF) to osteoblastic cells and quantifying real-time intracellular calcium [Ca2+]i, prostaglandin E2 (PGE2) release, and osteopontin (OPN) mRNA levels. Cells were exposed to OFF (1 Hz) at shear stresses of 1 and 2 Pa with rest periods of 5, 10, and 15s inserted every 10 loading cycles. The insertion of 10 and 15s rest periods into the flow profile resulted in multiple [Ca2+]i responses by individual cells, increased [Ca2+]i response magnitudes, and increased overall percent of cells responding compared to continuously loaded control groups. We determined the source of the multiple calcium responses to be from intracellular stores. In addition, rest inserted OFF led to similar levels of PGE2 release and increased levels of relative OPN mRNA compared to cells exposed to continuous OFF. Our study suggests that the cellular mechanism of bone adaptation to rest inserted mechanical loading may involve modulation of intracellular levels of calcium (frequency, magnitude, percent of cells responding).
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Affiliation(s)
- Nikhil N Batra
- Bone and Joint Rehabilitation R&D Center, Veterans Affairs Medical Center, Palo Alto, CA, USA
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4
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Nagasawa H, Peng Y, Wilson PF, Lio YC, Chen DJ, Bedford JS, Little JB. Role of homologous recombination in the alpha-particle-induced bystander effect for sister chromatid exchanges and chromosomal aberrations. Radiat Res 2005; 164:141-7. [PMID: 16038585 DOI: 10.1667/rr3420] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The bystander effect for sister chromatid exchanges (SCEs) and chromosomal aberrations was examined in hamster cell lines deficient in either DNA-PKcs (V3 cells, deficient in nonhomologous end joining, NHEJ) or RAD51C (irs3 cells, deficient in homologous recombination, HR). Cells synchronized in G0/G1 phase were irradiated with very low fluences of alpha particles such that < 1% of the nuclei were traversed by an alpha particle. Wild-type cells showed a prominent bystander response for SCE induction; an even greater effect was observed in V3 cells. On the other hand, no significant induction of SCE was observed in the irs3 RAD51C-deficient bystander cells irradiated at various stages in the cell cycle. Whereas a marked bystander effect for chromosomal aberrations occurred in V3 cells, the induction of chromosomal aberrations in irs3 bystander cells was minimal and similar to that of wild-type cells. Based on these findings, we hypothesize that HR is essential for the induction of SCE in bystander cells; however, HR is unable to repair the DNA damage induced in NHEJ-deficient bystander cells that leads to either SCE or chromosomal aberrations.
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Affiliation(s)
- H Nagasawa
- Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, Colorado 80523, USA
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5
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Abstract
Raf-1 plays important roles in cell proliferation, differentiation, and survival. However, the unique and essential function of Raf-1 is anti-apoptotic. The molecules that mediate Raf-1's anti-apoptotic function are not known. In the course of identifying new substrates of Raf-1, we found that the Raf-1 kinase domain interacted with apoptosis-linked gene-2 (ALG-2) in yeast two-hybrid system. Our further studies showed that Raf-1 phosphorylated ALG-2 in an in vitro kinase assay. We also found that apoptosis signal-regulating kinase 1 (ASK1) strongly phosphorylated ALG-2. Importantly, Raf-1 blocks the ASK1-dependent ALG-2 phosphorylation. Since ALG-2 associates with ASK1, and both ASK1 and ALG-2 are involved in apoptosis, our observations indicate that Raf-1 may mediate its anti-apoptotic function by interrupting ASK1-dependent phosphorylation of ALG-2.
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Affiliation(s)
- Changmin Chen
- Laboratory for Cell and Molecular Biology, Division of Hematology and Oncology, Beth Israel Deaconess Medical Center, Department of Medicine, Harvard Medical School, USA.
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6
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Affiliation(s)
- Donald E Ingber
- Harvard Medical School and Children's Hospital, Boston, MA 02115, USA.
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7
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Abstract
On demand, rapid Ca(2+)-triggered homotypic and exocytic membrane-fusion events are required to repair a torn plasma membrane, and we propose that this emergency-based fusion differs fundamentally from other rapid, triggered fusion reactions. Emergency fusion might use a specialized protein and organelle emergency response team that can simultaneously promote impromptu homotypic fusion events between organelles and exocytic fusion events along the vertices between these fusion products and the plasma membrane.
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Affiliation(s)
- Paul L McNeil
- Department of Anatomy and Cellular Biology, Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, Georgia 30921, USA.
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8
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Abstract
Previous studies have explored the link between bone regeneration and skeletogenesis. Although a great deal is known regarding tissue and cell based events, especially those involving ossification and chondrogenesis, much remains unknown about the molecular similarity of repair and development. Since the functional significance of Homeobox (Hox) genes in embryonic skeletogenesis has been well documented through knockout and deficiency studies, we chose to investigate whether members of this family are reactivated during fracture repair. Specifically, we examined the temporal and spatial expression of Msx-1, Msx-2, rHox, Hoxa-2 and Hoxd-9, because of their involvement in limb development. Utilizing quantitative reverse transcriptase RT-PCR (qPCR), mRNA levels from all five genes were shown to be upregulated during fracture repair at all times tested (post-fracture day 3-21), as compared to intact bone. Further, using in situ hybridization and immunohistochemistry, spatial expression of these genes was localized to osteoblasts, chondrocytes and periosteal osteoprogenitor cells found within the fracture callus, the foremost cells responsible for the reparative phase of the healing process. Given the contribution of Hox genes in skeletal development, our results suggest that these genes are involved in either the patterning or formation of the fracture callus, further supporting the notion that bone regeneration recapitulates skeletal development.
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Affiliation(s)
- Robert P Gersch
- Department of Biomedical Engineering, Stony Brook University, Psychology A Building, Stony Brook, NY 11794-2580, USA
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9
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Li L, Roden J, Shapiro BE, Wold BJ, Bhatia S, Forman SJ, Bhatia R. Reproducibility, fidelity, and discriminant validity of mRNA amplification for microarray analysis from primary hematopoietic cells. J Mol Diagn 2005; 7:48-56. [PMID: 15681474 PMCID: PMC1867503 DOI: 10.1016/s1525-1578(10)60008-6] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Analysis of gene expression in clinical samples poses special challenges, including limited RNA availability and poor RNA quality. Quantitative information regarding reliability of RNA amplification methodologies applied to primary cells and representativeness of resulting gene expression profiles is limited. We evaluated four protocols for RNA amplification from peripheral blood mononuclear cells. Results obtained with 100 ng or 10 ng of RNA amplified using two rounds of cDNA synthesis and in vitro transcription were compared with control 2.5-microg RNA samples processed using a single round of in vitro transcription. Samples were hybridized to Affymetrix HG-U133A arrays. Considerable differences in results were obtained with different protocols. The optimal protocol resulted in highly reproducible gene expression profiles from amplified samples (r = 0.98) and good correlation between amplified and control samples (r = 0.94). Using the optimal protocol dissimilarities of gene expression between mononuclear cells from a normal individual and a patient with myelodysplastic syndrome were primarily maintained after amplification compared with controls. We conclude that small variations in methodology introduce considerable distortion of gene expression profiles obtained after RNA amplification from clinical samples and too strong a focus on a very small number of genes picked from an array analysis could be unduly influenced by seemingly acceptable methodologies. However, it is possible to obtain reproducible and representative results using optimized protocols.
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Affiliation(s)
- Liang Li
- Division of Hematology and Bone Marrow Transplantation, City of Hope National Medical Center, 1500 East Duarte Rd., Duarte, CA 91010, USA
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10
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Abstract
The power for appreciating complex cellular interactions during embryonic development using green fluorescent protein (GFP) as a visual histological marker has not been applied to adult tissues due to loss of GFP signal during paraffin embedding and a high autofluorescent background, particularly in section of bone and bone marrow. Here we demonstrate that the GFP signal is well preserved in frozen sections of adult decalcified bone. Using a tape-transfer system that preserves histological relationships, GFP expression can be related to standard histological stains used in bone biology research. The choice of a dual-filter cube and a strong GFP signal makes it possible to readily distinguish at least four different GFP colors that are distinctly different from the autofluorescent background. An additional advantage of the frozen sections is better preservation of immunological epitopes that allow colocalization of an immunostained section with an endogenous GFP and a strong lacZ signal emanating from a beta-gal marker gene. We present an approach for recording multiple images from the same histological section that allows colocalization of a GFP signal with subsequent stains and procedures that destroy GFP. Examples that illustrate the flexibility for dual imaging of various fluorescent signals are described in this study. The same imaging approach can serve as a vehicle for archiving, retrieving, and sharing histological images among research groups.
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Affiliation(s)
- Xi Jiang
- Department of Genetics and Development Biology, University of Connecticut Health Center, Farmington, CT 06030, USA
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11
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Kumei Y, Morita S, Nakamura H, Katano H, Ohya K, Shimokawa H, Sams CF, Whitson PA. Osteoblast responsiveness to 1alpha,25-dihydroxyvitamin D3 during spaceflight. Ann N Y Acad Sci 2005; 1030:121-4. [PMID: 15659788 DOI: 10.1196/annals.1329.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Rat osteoblasts were cultured aboard a space shuttle for 4 and 5 days. Cells were treated with 1 nM 1alpha,25-dihydroxyvitamin D(3) (VD) for the last 1 day. The conditioned media were harvested. Cells were solubilized with guanidine solution on board. We examined microgravity effects on the production/expression of osteocalcin, bone sialoprotein (BSP), and VD receptor (VD-R) in osteoblasts. Under VD treatment, the osteocalcin protein level was 243 +/- 117 and 1,718 +/- 534 pg/microg cellular DNA in flight cultures and ground controls, respectively. Without VD treatment, the osteocalcin protein level was not different between flight cultures and ground controls. The osteocalcin mRNA level in the VD-treated flight cultures was as low as 16% of that in ground controls. The VD-R mRNA level in the VD-treated flight cultures was also decreased to 16% of that in ground controls. Microgravity would suppress the VD-inducible production of osteocalcin but not the basal productivity. The BSP mRNA level was increased by microgravity. VD/VD-R binds to the vitamin D-responsive element (VDRE) on the target genes. The rat osteocalcin gene is positively regulated via "enhancer" VDRE, whereas the rat BSP gene is negatively regulated via "repressor " VDRE. Microgravity might modulate osteoblast responsiveness to VD through the suppression of VD-R.
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Affiliation(s)
- Yasuhiro Kumei
- Department of Hard Tissue Engineering, Graduate School of Tokyo Medical and Dental University, Tokyo 113-8549, Japan.
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12
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Abstract
The tension-driven gating transition in the large mechanosensitive channel MscL proceeds through detectable states of intermediate conductance. Gain-of-function (GOF) mutants with polar or charged substitutions in the main hydrophobic gate display altered patterns of subconducting states, providing valuable information about gating intermediates. Here we present thermodynamic analysis of several GOF mutants to clarify the nature and position of low-conducting conformations in the transition pathway. Unlike wild-type (WT) MscL, which predominantly occupies the closed and fully open states with very brief substates, the mild V23T GOF mutant frequently visits a multitude of short-lived subconducting states. Severe mutants V23D and G22N open in sequence: closed (C) --> low-conducting substate (S) --> open (O), with the first subtransition occurring at lower tensions. Analyses of equilibrium state occupancies as functions of membrane tension show that the C-->S subtransition in WT MscL is associated with only a minor conductance increment, but the largest in-plane expansion and free energy change. The GOF substitutions strongly affect the first subtransition by reducing area ((Delta)A) and energy ((Delta)E) changes between C and S states commensurably with the severity of mutation. GOF mutants also exhibited a considerably larger (Delta)E associated with the second (S-->O) subtransition, but a (Delta)A similar to WT. The area changes indicate that closed conformations of GOF mutants are physically preexpanded. The tension dependencies of rate constants for channel closure (k(off)) predict different positions of rate-limiting barriers on the energy-area profiles for WT and GOF MscL. The data support the two-gate mechanism in which the first subtransition (C-->S) can be viewed as opening of the central (M1) gate, resulting in an expanded water-filled "leaky" conformation. Strong facilitation of this step by polar GOF substitutions suggests that separation of M1 helices associated with hydration of the pore in WT MscL is the major energetic barrier for opening. Mutants with a stabilized S1 gate demonstrate impeded transitions from low-conducting substates to the fully open state, whereas extensions of S1-M1 linkers result in a much higher probability of reverse O-->S transitions. These data strongly suggest that the bulk of conductance gain in the second subtransition (S-->O) occurs through the opening of the NH2-terminal (S1) gate and the linkers are coupling elements between the M1 and S1 gates.
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Affiliation(s)
- Andriy Anishkin
- Department of Biology, University of Maryland, College Park, MD 20742, USA
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13
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Xu K, Feldman L, Davis KL, Sytkowski AJ. Erythropoietin and IL-3 receptor cell surface expression is decreased under conditions that model some aspects of microgravity. Gravit Space Biol Bull 2005; 18:111-2. [PMID: 16044632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Affiliation(s)
- Kun Xu
- Laboratory for Cell and Molecular Biology, Division of Hematology and Oncology, Beth Israel Deaconess Medical Center, Department of Medicine, Harvard Medical School, Boston, MA 02215, USA
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14
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Zhong N, Garman RA, Squire ME, Donahue LR, Rubin CT, Hadjiargyrou M, Judex S. Gene expression patterns in bone after 4 days of hind-limb unloading in two inbred strains of mice. Aviat Space Environ Med 2005; 76:530-5. [PMID: 15945395] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
INTRODUCTION An improved understanding of the interdependence of transcriptional and genomic control of bone loss is critical for the design of effective and safe countermeasures for osteoporosis in space and on Earth. In an effort to test whether molecular pathways modulating the loss of functional weight bearing are dependent on genetic makeup, we quantified the differential expression of genes critical to the early stages of bone remodeling in two different strains of mice. METHODS Adult (4-mo-old) female BALB/cByJ (BALB) and C3H/HeJ (C3H) mice, strains with different sensitivities to unloading, were subjected to hind-limb unloading (HLU) or normal cage activities. RNA was extracted from the tibia following 4 d of HLU and expression levels were determined. RESULTS In the BALB mice, HLU significantly altered transcriptional levels of osterix (-36%), alkaline phosphatase (-36%), osteonectin (-44%), collagen type 1 (-55%), MMP2 (-36%), osteocalcin (-68%), and osteopontin (+28%). This expression pattern was highly correlated (R2 = 0.75) with altered expression levels in the C3H mice, but the magnitude of altered mRNA levels was less than half of those in the BALB mice. These strain-specific changes in gene expression were consistent with the differential changes in bone formation, as determined in a second group of BALB and C3H mice. DISCUSSION AND CONCLUSIONS These data indicate that genetics may influence the absolute changes in gene expression of genes during spaceflight, but that the molecular pathways targeted by countermeasures of bone loss may not need to be specific to an individual's genetic makeup.
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Affiliation(s)
- Nan Zhong
- Department of Biomedical Engineering, State University of New York, Stony Brook, NY 11794-2580, USA
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15
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Duke PJ, Callejas W, Doan L, Marsh M. Phototaxis and aerotaxis in a calcifying alga. Gravit Space Biol Bull 2005; 18:115-6. [PMID: 16044634] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Affiliation(s)
- P Jackie Duke
- Dept. of Orthodontics, Dental Branch, University of Texas Health Science Center at Houston, USA
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16
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Affiliation(s)
- Natasha Raikhel
- Botany and Plant Sciences Department , University of California, Riverside, California 92521, USA.
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17
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Affiliation(s)
- Thomas Girke
- Center for Plant Cell Biology, Department of Botany and Plant Sciences, University of California, Riverside, California 92521, USA.
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18
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Guadarrama S, Pulcini ED, Broadaway SC, Pyle BH. Pseudomonas aeruginosa growth and production of Exotoxin A in static and modeled microgravity environments. Gravit Space Biol Bull 2005; 18:85-6. [PMID: 16038097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Affiliation(s)
- S Guadarrama
- Department of Microbiology, Montana State University-Bozeman, MT 59717, USA
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19
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Blumberg S, Gajraj A, Pennington MW, Meiners JC. Three-dimensional characterization of tethered microspheres by total internal reflection fluorescence microscopy. Biophys J 2005; 89:1272-81. [PMID: 15923224 PMCID: PMC1366611 DOI: 10.1529/biophysj.105.061242] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Tethered particle microscopy is a powerful tool to study the dynamics of DNA molecules and DNA-protein complexes in single-molecule experiments. We demonstrate that stroboscopic total internal reflection microscopy can be used to characterize the three-dimensional spatiotemporal motion of DNA-tethered particles. By calculating characteristic measures such as symmetry and time constants of the motion, well-formed tethers can be distinguished from defective ones for which the motion is dominated by aberrant surface effects. This improves the reliability of measurements on tether dynamics. For instance, in observations of protein-mediated DNA looping, loop formation is distinguished from adsorption and other nonspecific events.
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Affiliation(s)
- Seth Blumberg
- Department of Physics, Biophysics Research Division, Randall Laboratory, University of Michigan, Ann Arbor, 48109-1120, USA
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20
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Heisterkamp A, Maxwell IZ, Mazur E, Underwood JM, Nickerson JA, Kumar S, Ingber DE. Pulse energy dependence of subcellular dissection by femtosecond laser pulses. Opt Express 2005; 13:3690-6. [PMID: 16035172 DOI: 10.1364/opex.13.003690] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Precise dissection of cells with ultrashort laser pulses requires a clear understanding of how the onset and extent of ablation (i.e., the removal of material) depends on pulse energy. We carried out a systematic study of the energy dependence of the plasma-mediated ablation of fluorescently-labeled subcellular structures in the cytoskeleton and nuclei of fixed endothelial cells using femtosecond, near-infrared laser pulses focused through a high-numerical aperture objective lens (1.4 NA). We find that the energy threshold for photobleaching lies between 0.9 and 1.7 nJ. By comparing the changes in fluorescence with the actual material loss determined by electron microscopy, we find that the threshold for true material ablation is about 20% higher than the photobleaching threshold. This information makes it possible to use the fluorescence to determine the onset of true material ablation without resorting to electron microscopy. We confirm the precision of this technique by severing a single microtubule without disrupting the neighboring microtubules, less than 1 micrometer away.
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Affiliation(s)
- A Heisterkamp
- Department of Engineering and Applied Science, Harvard University, Cambridge, MA 02138, USA.
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21
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Hart CE, Sharenbroich L, Bornstein BJ, Trout D, King B, Mjolsness E, Wold BJ. A mathematical and computational framework for quantitative comparison and integration of large-scale gene expression data. Nucleic Acids Res 2005; 33:2580-94. [PMID: 15886390 PMCID: PMC1092273 DOI: 10.1093/nar/gki536] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Analysis of large-scale gene expression studies usually begins with gene clustering. A ubiquitous problem is that different algorithms applied to the same data inevitably give different results, and the differences are often substantial, involving a quarter or more of the genes analyzed. This raises a series of important but nettlesome questions: How are different clustering results related to each other and to the underlying data structure? Is one clustering objectively superior to another? Which differences, if any, are likely candidates to be biologically important? A systematic and quantitative way to address these questions is needed, together with an effective way to integrate and leverage expression results with other kinds of large-scale data and annotations. We developed a mathematical and computational framework to help quantify, compare, visualize and interactively mine clusterings. We show that by coupling confusion matrices with appropriate metrics (linear assignment and normalized mutual information scores), one can quantify and map differences between clusterings. A version of receiver operator characteristic analysis proved effective for quantifying and visualizing cluster quality and overlap. These methods, plus a flexible library of clustering algorithms, can be called from a new expandable set of software tools called CompClust 1.0 (http://woldlab.caltech.edu/compClust/). CompClust also makes it possible to relate expression clustering patterns to DNA sequence motif occurrences, protein-DNA interaction measurements and various kinds of functional annotations. Test analyses used yeast cell cycle data and revealed data structure not obvious under all algorithms. These results were then integrated with transcription motif and global protein-DNA interaction data to identify G1 regulatory modules.
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Affiliation(s)
| | - Lucas Sharenbroich
- Jet Propulsion Laboratory, Machine Learning Systems GroupPasadena, CA 91109, USA
| | | | | | | | - Eric Mjolsness
- Institute for Genomics and Bioinformatics, University of CaliforniaIrvine, Irvine, CA 92697, USA
- School of Information and Computer Science, University of CaliforniaIrvine, Irvine, CA 92697, USA
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22
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Abstract
Several reports show that the nucleus is 10 times stiffer than the cytoplasm. Hence, it is not clear if intra-nuclear structures can be directly deformed by a load of physiologic magnitudes. If a physiologic load could not directly deform intra-nuclear structures, then signaling inside the nucleus would occur only via the mechanisms of diffusion or translocation. Using a synchronous detection approach, we quantified displacements of nucleolar structures in cultured airway smooth muscle cells in response to a localized physiologic load ( approximately 0.4 microm surface deformation) via integrin receptors. The nucleolus exhibited significant displacements. Nucleolar structures also exhibited significant deformation, with the dominant strain being the bulk strain. Increasing the pre-existing tensile stress (prestress) in the cytoskeleton significantly increased the stress propagation efficiency to the nucleolus (defined as nucleolus displacement per surface deformation) whereas decreasing the prestress significantly lowered the stress propagation efficiency to the nucleolus. Abolishing the stress fibers/actin bundles by plating the cells on poly-L-lysine-coated dishes dramatically inhibited stress propagation to the nucleolus. These results demonstrate that the prestress in the cytoskeleton is crucial in mediating stress propagation to the nucleolus, with implications for direct mechanical regulation of nuclear activities and functions.
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Affiliation(s)
- Shaohua Hu
- Physiology Program, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115, USA
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Hughes-Fulford M, Tjandrawinata RR, Li CF, Sayyah S. Arachidonic acid, an omega-6 fatty acid, induces cytoplasmic phospholipase A2 in prostate carcinoma cells. Carcinogenesis 2005; 26:1520-6. [PMID: 15878913 DOI: 10.1093/carcin/bgi112] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
For the past 60 years, dietary intake of essential fatty acids has increased. Moreover, the omega-6 fatty acids have recently been found to play an important role in regulation of gene expression. Proliferation of human prostate cells was significantly increased 48 h after arachidonic acid (AA) addition. We have analyzed initial uptake using nile red fluorescence and we found that the albumin conjugated AA is endocytosed into the cells followed by the induction of RNA within minutes, protein and PGE2 synthesis within hours. Here we describe that AA induces expression of cytosolic phospholipase A2 (cPLA2) in a dose-dependent manner and that this upregulation is dependent upon downstream synthesis of PGE2. The upregulation of cox-2 and cPLA2 was inhibited by flurbiprofen, a cyclooxygenase (COX) inhibitor, making this a second feed-forward enzyme in the eicosanoid pathway. Cox-2 specific inhibitors are known to inhibit colon and prostate cancer growth in humans; however, recent findings show that some of these have cardiovascular complications. Since cPLA2 is upstream in the eicosanoid pathway, it may be a good alternative for a pharmaceutical target for the treatment of cancer.
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Affiliation(s)
- Millie Hughes-Fulford
- Laboratory of Cell Growth, Mail Code 151F, Department of Medicine, Northern California Institute for Research and Education and Veterans Affairs Medical Center, University of California, San Francisco, CA 94121, USA.
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Abstract
A fundamental question in the field of mechanotransduction is how forces propagate inside a cell. Recent experiments have shown that a force of a physiological magnitude, applied via a focal adhesion, can propagate a long distance into the cell. This observation disagrees with existing models that regard the cell as a homogeneous body. We show that this "action at a distance" results from the inhomogeneity in the cell: a prestressed and stiff actin bundle guides the propagation of forces over long distances. Our models highlight the enormous ratios of the prestress and the modulus of the actin bundle to the modulus of the cytoskeleton network. For a normal cell, the models predict that forces propagate over characteristic lengths comparable to the size of the cell. The characteristic lengths can be altered, however, by treatments of the cell. We provide experimental evidence and discuss biological implications.
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Affiliation(s)
- Ning Wang
- Physiology Program, Harvard School of Public Health, Boston, MA 02115, USA.
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25
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Huang S, Eichler G, Bar-Yam Y, Ingber DE. Cell fates as high-dimensional attractor states of a complex gene regulatory network. Phys Rev Lett 2005; 94:128701. [PMID: 15903968 DOI: 10.1103/physrevlett.94.128701] [Citation(s) in RCA: 425] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2004] [Indexed: 05/02/2023]
Abstract
Cells in multicellular organisms switch between distinct cell fates, such as proliferation or differentiation into specialized cell types. Genome-wide gene regulatory networks govern this behavior. Theoretical studies of complex networks suggest that they can exhibit ordered (stable) dynamics, raising the possibility that cell fates may represent high-dimensional attractor states. We used gene expression profiling to show that trajectories of neutrophil differentiation converge to a common state from different directions of a 2773-dimensional gene expression state space, providing the first experimental evidence for a high-dimensional stable attractor that represents a distinct cellular phenotype.
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Affiliation(s)
- Sui Huang
- Vascular Biology Program, Departments of Pathology & Surgery, Children's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
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26
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David S, Kalb RG. Serum/glucocorticoid-inducible kinase can phosphorylate the cyclic AMP response element binding protein, CREB. FEBS Lett 2005; 579:1534-8. [PMID: 15733869 DOI: 10.1016/j.febslet.2005.01.040] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2004] [Revised: 12/01/2004] [Accepted: 01/19/2005] [Indexed: 11/24/2022]
Abstract
To maintain homeostasis, cells often respond to stressful extra-cellular stimuli by new gene expression. Serum/glucocorticoid-induced kinase (SGK) is an immediate early gene whose expression is induced by a variety of extra-cellular stimuli. Here, we examine the possibility that SGK can directly phosphorylate the transcription factor cyclic AMP response element binding protein (CREB). In a cell-free context, SGK physically associates with CREB and SGK phosphorylates it on serine 133. Phospho-serine 133 is essential for stimulating the transcriptional activity of CREB. Further, we show that in a variety of cellular contexts, SGK phosphorylates CREB. Activation of receptor tyrosine kinase pathways or the phosphoinositide-dependent kinase 1 (PDK1) lead to SGK-dependent CREB phosphorylation. Hormonal stimulation of epithelial cells leads to the induction of endogenous SGK and CREB phosphorylation. A dominant-negative form of SGK blocks dexamethasone-induced CREB phosphorylation. Our studies indicate that stimulation of SGK can lead to CREB phosphorylation, suggesting that CREB-dependent gene transcription is an important link between stressful extra-cellular signals and cellular responses.
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Affiliation(s)
- Samuel David
- Children's Hospital of Philadelphia, Joseph Stokes Jr. Research Institute, ARC 814, 3615 Civic Center Boulevard, Philadelphia, PA 19104, USA
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27
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Stolc V, Samanta MP, Tongprasit W, Sethi H, Liang S, Nelson DC, Hegeman A, Nelson C, Rancour D, Bednarek S, Ulrich EL, Zhao Q, Wrobel RL, Newman CS, Fox BG, Phillips GN, Markley JL, Sussman MR. Identification of transcribed sequences in Arabidopsis thaliana by using high-resolution genome tiling arrays. Proc Natl Acad Sci U S A 2005; 102:4453-8. [PMID: 15755812 PMCID: PMC555476 DOI: 10.1073/pnas.0408203102] [Citation(s) in RCA: 127] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2004] [Indexed: 11/18/2022] Open
Abstract
Using a maskless photolithography method, we produced DNA oligonucleotide microarrays with probe sequences tiled throughout the genome of the plant Arabidopsis thaliana. RNA expression was determined for the complete nuclear, mitochondrial, and chloroplast genomes by tiling 5 million 36-mer probes. These probes were hybridized to labeled mRNA isolated from liquid grown T87 cells, an undifferentiated Arabidopsis cell culture line. Transcripts were detected from at least 60% of the nearly 26,330 annotated genes, which included 151 predicted genes that were not identified previously by a similar genome-wide hybridization study on four different cell lines. In comparison with previously published results with 25-mer tiling arrays produced by chromium masking-based photolithography technique, 36-mer oligonucleotide probes were found to be more useful in identifying intron-exon boundaries. Using two-dimensional HPLC tandem mass spectrometry, a small-scale proteomic analysis was performed with the same cells. A large amount of strongly hybridizing RNA was found in regions "antisense" to known genes. Similarity of antisense activities between the 25-mer and 36-mer data sets suggests that it is a reproducible and inherent property of the experiments. Transcription activities were also detected for many of the intergenic regions and the small RNAs, including tRNA, small nuclear RNA, small nucleolar RNA, and microRNA. Expression of tRNAs correlates with genome-wide amino acid usage.
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MESH Headings
- Arabidopsis/genetics
- Arabidopsis Proteins/genetics
- Arabidopsis Proteins/isolation & purification
- Base Sequence
- Chromatography, High Pressure Liquid
- DNA, Complementary/genetics
- DNA, Plant/genetics
- Exons
- Gene Expression Profiling
- Genome, Plant
- Introns
- Oligonucleotide Array Sequence Analysis/methods
- Optics and Photonics
- Photography/methods
- Proteomics/methods
- RNA, Antisense/analysis
- RNA, Antisense/genetics
- RNA, Messenger/analysis
- RNA, Messenger/genetics
- RNA, Plant/analysis
- RNA, Plant/genetics
- Reverse Transcriptase Polymerase Chain Reaction
- Spectrometry, Mass, Electrospray Ionization
- Transcription, Genetic
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Affiliation(s)
- Viktor Stolc
- Genome Research Facility, National Aeronautics and Space Administration Ames Research Center, Moffett Field, CA 94035, USA
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28
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Atsawasuwan P, Mochida Y, Parisuthiman D, Yamauchi M. Expression of lysyl oxidase isoforms in MC3T3-E1 osteoblastic cells. Biochem Biophys Res Commun 2005; 327:1042-6. [PMID: 15652501 DOI: 10.1016/j.bbrc.2004.12.119] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2004] [Indexed: 11/17/2022]
Abstract
Covalent intermolecular cross-linking of collagen is initiated by the action of lysyl oxidase (LOX) on the telopeptidyl lysine and hydroxylysine residues. Recently, several LOX isoforms, i.e., LOX-like proteins 1-4 (LOXL1-4), have been identified but their specific tissue distribution and functions are still largely unknown. In this study, mRNA expression of LOX and LOXL1-4 in MC3T3-E1 osteoblastic cells was screened by RT-PCR and quantitatively analyzed by real-time PCR during cell differentiation and matrix mineralization. The results demonstrated that LOX and all LOXLs, except LOXL2, were expressed in this cell line and that the expression pattern during cell differentiation and matrix mineralization was distinct from one another. This indicates that the expression of LOX and its isoforms is highly regulated during osteoblast differentiation, suggesting their distinct roles in collagen matrix stabilization and subsequent mineralization.
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Affiliation(s)
- Phimon Atsawasuwan
- CB#7455, Dental Research Center, University of North Carolina at Chapel Hill, NC 27599-7455, USA
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29
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30
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Carterson AJ, Höner zu Bentrup K, Ott CM, Clarke MS, Pierson DL, Vanderburg CR, Buchanan KL, Nickerson CA, Schurr MJ. A549 lung epithelial cells grown as three-dimensional aggregates: alternative tissue culture model for Pseudomonas aeruginosa pathogenesis. Infect Immun 2005; 73:1129-40. [PMID: 15664956 PMCID: PMC547019 DOI: 10.1128/iai.73.2.1129-1140.2005] [Citation(s) in RCA: 156] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A three-dimensional (3-D) lung aggregate model was developed from A549 human lung epithelial cells by using a rotating-wall vessel bioreactor to study the interactions between Pseudomonas aeruginosa and lung epithelial cells. The suitability of the 3-D aggregates as an infection model was examined by immunohistochemistry, adherence and invasion assays, scanning electron microscopy, and cytokine and mucoglycoprotein production. Immunohistochemical characterization of the 3-D A549 aggregates showed increased expression of epithelial cell-specific markers and decreased expression of cancer-specific markers compared to their monolayer counterparts. Immunohistochemistry of junctional markers on A549 3-D cells revealed that these cells formed tight junctions and polarity, in contrast to the cells grown as monolayers. Additionally, the 3-D aggregates stained positively for the production of mucoglycoprotein while the monolayers showed no indication of staining. Moreover, mucin-specific antibodies to MUC1 and MUC5A bound with greater affinity to 3-D aggregates than to the monolayers. P. aeruginosa attached to and penetrated A549 monolayers significantly more than the same cells grown as 3-D aggregates. Scanning electron microscopy of A549 cells grown as monolayers and 3-D aggregates infected with P. aeruginosa showed that monolayers detached from the surface of the culture plate postinfection, in contrast to the 3-D aggregates, which remained attached to the microcarrier beads. In response to infection, proinflammatory cytokine levels were elevated for the 3-D A549 aggregates compared to monolayer controls. These findings suggest that A549 lung cells grown as 3-D aggregates may represent a more physiologically relevant model to examine the interactions between P. aeruginosa and the lung epithelium during infection.
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Affiliation(s)
- A J Carterson
- Department of Microbiology and Immunology, Program in Molecular Pathogenesis and Immunity, Tulane University Health Sciences Center, 1430 Tulane Avenue, New Orleans, LA 70112, USA
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31
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Cerny J, Feng Y, Yu A, Miyake K, Borgonovo B, Klumperman J, Meldolesi J, McNeil PL, Kirchhausen T. The small chemical vacuolin-1 inhibits Ca(2+)-dependent lysosomal exocytosis but not cell resealing. EMBO Rep 2005; 5:883-8. [PMID: 15332114 PMCID: PMC1299144 DOI: 10.1038/sj.embor.7400243] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2004] [Revised: 07/09/2004] [Accepted: 07/29/2004] [Indexed: 11/08/2022] Open
Abstract
Resealing after wounding, the process of repair following plasma membrane damage, requires exocytosis. Vacuolins are molecules that induce rapid formation of large, swollen structures derived from endosomes and lysosomes by homotypic fusion combined with uncontrolled fusion of the inner and limiting membranes of these organelles. Vacuolin-1, the most potent compound, blocks the Ca(2+)-dependent exocytosis of lysosomes induced by ionomycin or plasma membrane wounding, without affecting the process of resealing. In contrast, other cell structures and membrane trafficking functions including exocytosis of enlargeosomes are unaffected. Because cells heal normally in the presence of vacuolin-1, we suggest that lysosomes are dispensable for resealing.
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Affiliation(s)
- Jan Cerny
- Department of Cell Biology and The CBR Institute for Biomedical Research, Harvard Medical School, Boston, Massachusetts 02115, USA
- Department of Physiology of Animals and Developmental Biology, Charles University, Prague 2, Czech Republic
| | - Yan Feng
- Institute of Chemistry and Cell Biology, ICCB, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Anan Yu
- Department of Cell Biology and The CBR Institute for Biomedical Research, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Katsuya Miyake
- Department of Cellular Biology and Anatomy and Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, Georgia 30912, USA
| | - Barbara Borgonovo
- Department of Neuroscience, DIBIT, Vitasalute San Raffaele University and San Raffaele Institute, Via Olgettina 58, 20132 Milano, Italy
| | - Judith Klumperman
- Department of Cell Biology, University Medical Centre and Institute for Biomembranes, Heidelberglaan 100, 3584 Utrecht, The Netherlands
| | - Jacopo Meldolesi
- Department of Neuroscience, DIBIT, Vitasalute San Raffaele University and San Raffaele Institute, Via Olgettina 58, 20132 Milano, Italy
| | - Paul L McNeil
- Department of Cellular Biology and Anatomy and Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, Georgia 30912, USA
| | - Tomas Kirchhausen
- Department of Cell Biology and The CBR Institute for Biomedical Research, Harvard Medical School, Boston, Massachusetts 02115, USA
- Institute of Chemistry and Cell Biology, ICCB, Harvard Medical School, Boston, Massachusetts 02115, USA
- Tel: +1 617 278 3140; Fax: +1 617 278 3131; E-mail:
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32
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Stolc V, Samanta MP, Tongprasit W, Marshall WF. Genome-wide transcriptional analysis of flagellar regeneration in Chlamydomonas reinhardtii identifies orthologs of ciliary disease genes. Proc Natl Acad Sci U S A 2005; 102:3703-7. [PMID: 15738400 PMCID: PMC553310 DOI: 10.1073/pnas.0408358102] [Citation(s) in RCA: 179] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The important role that cilia and flagella play in human disease creates an urgent need to identify genes involved in ciliary assembly and function. The strong and specific induction of flagellar-coding genes during flagellar regeneration in Chlamydomonas reinhardtii suggests that transcriptional profiling of such cells would reveal new flagella-related genes. We have conducted a genome-wide analysis of RNA transcript levels during flagellar regeneration in Chlamydomonas by using maskless photolithography method-produced DNA oligonucleotide microarrays with unique probe sequences for all exons of the 19,803 predicted genes. This analysis represents previously uncharacterized whole-genome transcriptional activity profiling study in this important model organism. Analysis of strongly induced genes reveals a large set of known flagellar components and also identifies a number of important disease-related proteins as being involved with cilia and flagella, including the zebrafish polycystic kidney genes Qilin, Reptin, and Pontin, as well as the testis-expressed tubby-like protein TULP2.
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Affiliation(s)
- Viktor Stolc
- Genome Research Facility, National Aeronautic and Space Administration, Ames Research Center, Moffett Field, CA 94035, USA.
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33
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Hughes-Fulford M, Sugano E, Schopper T, Li CF, Boonyaratanakornkit JB, Cogoli A. Early immune response and regulation of IL-2 receptor subunits. Cell Signal 2005; 17:1111-24. [PMID: 15993752 DOI: 10.1016/j.cellsig.2004.12.016] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2004] [Revised: 09/29/2004] [Accepted: 12/11/2004] [Indexed: 10/25/2022]
Abstract
Affymetrix oligonucleotide arrays were used to monitor expression of 8796 genes and probe sets in activated T-cells; analysis revealed that 217 genes were significantly upregulated within 4 h. Induced genes included transcription factors, cytokines and their receptor genes. Analysis by semi-quantitative RT-PCR confirmed the significant induction of IL-2, IL-2R(gamma) and IL-2R(alpha). Forty-eight of the 217 induced genes are known to or predicted to be regulated by a CRE promoter/enhancer. We found that T-cell activation caused a significant increase in CREB phosphorylation furthermore, inhibition of the PKC pathway by GF109203 reduced CREB activation by 50% and inhibition of the PKA pathway caused a total block of CREB phosphorylation and significantly reduced IFN(gamma), IL-2 and IL-2R(alpha) gene expression by approximately 40% (p<0.001). PKC(theta) plays a major role in T-cell activation: inhibition of PKC significantly reduced the expression of IFN(gamma), IL-2 and IL-2R(alpha). Since PKC blocked activation of CREB, we studied potential cross-talk between the PKC and the PKA/MAPK pathways, PMA-stimulated Jurkat cells were studied with specific signal pathway inhibitors. Extracellular signal-regulated kinase-2 (ERK2) pathway was found to be significantly activated greater than seven-fold within 30 min; however, there was little activation of ERK-1 and no activation of JNK or p38 MAPK. Inhibition of the PKA pathway, but not the PKC pathway, resulted in inhibition of ERK1/2 activation at all time points, inhibition of MEK1 and 2 significantly blocked expression of IL-2 and IL-2R(alpha). Gene expression of IL-2R(alpha) and IFN(gamma) was dependent on PKA in S49 wt cells but not in kin- mutants. Using gel shift analysis, we found that forskolin activation of T-cells resulted in activation of AP1 sites; this increase in nuclear extract AP1 was significantly blocked by MEK1 inhibitor U0126. Taken together, these results suggest that the PKA in addition to PKC and MAPK pathways plays a role in early T-cell activation and induction of IL-2, IL-2R(alpha) and IFN(gamma) gene expression.
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Affiliation(s)
- Millie Hughes-Fulford
- Northern California Institute for Research and Education, San Francisco, CA, United States.
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34
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Elefteriou F, Ahn JD, Takeda S, Starbuck M, Yang X, Liu X, Kondo H, Richards WG, Bannon TW, Noda M, Clement K, Vaisse C, Karsenty G. Leptin regulation of bone resorption by the sympathetic nervous system and CART. Nature 2005; 434:514-20. [PMID: 15724149 DOI: 10.1038/nature03398] [Citation(s) in RCA: 839] [Impact Index Per Article: 44.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2004] [Accepted: 01/25/2005] [Indexed: 12/24/2022]
Abstract
Bone remodelling, the mechanism by which vertebrates regulate bone mass, comprises two phases, namely resorption by osteoclasts and formation by osteoblasts; osteoblasts are multifunctional cells also controlling osteoclast differentiation. Sympathetic signalling via beta2-adrenergic receptors (Adrb2) present on osteoblasts controls bone formation downstream of leptin. Here we show, by analysing Adrb2-deficient mice, that the sympathetic nervous system favours bone resorption by increasing expression in osteoblast progenitor cells of the osteoclast differentiation factor Rankl. This sympathetic function requires phosphorylation (by protein kinase A) of ATF4, a cell-specific CREB-related transcription factor essential for osteoblast differentiation and function. That bone resorption cannot increase in gonadectomized Adrb2-deficient mice highlights the biological importance of this regulation, but also contrasts sharply with the increase in bone resorption characterizing another hypogonadic mouse with low sympathetic tone, the ob/ob mouse. This discrepancy is explained, in part, by the fact that CART ('cocaine amphetamine regulated transcript'), a neuropeptide whose expression is controlled by leptin and nearly abolished in ob/ob mice, inhibits bone resorption by modulating Rankl expression. Our study establishes that leptin-regulated neural pathways control both aspects of bone remodelling, and demonstrates that integrity of sympathetic signalling is necessary for the increase in bone resorption caused by gonadal failure.
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MESH Headings
- Activating Transcription Factor 4
- Amino Acid Sequence
- Animals
- Bone Resorption
- Carrier Proteins/genetics
- Carrier Proteins/metabolism
- Cell Line
- Child
- Child, Preschool
- Cyclic AMP-Dependent Protein Kinases/metabolism
- Gene Deletion
- Humans
- Leptin/genetics
- Leptin/metabolism
- Leptin/pharmacology
- Male
- Membrane Glycoproteins/genetics
- Membrane Glycoproteins/metabolism
- Mice
- Models, Neurological
- Neoplasm Proteins/metabolism
- Nerve Tissue Proteins/deficiency
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/metabolism
- Osteoblasts/metabolism
- Osteogenesis
- RANK Ligand
- Receptor Activator of Nuclear Factor-kappa B
- Receptor, Melanocortin, Type 4/deficiency
- Receptor, Melanocortin, Type 4/genetics
- Receptors, Adrenergic, beta-2/deficiency
- Receptors, Adrenergic, beta-2/genetics
- Receptors, Leptin
- Response Elements/genetics
- Signal Transduction/drug effects
- Sympathetic Nervous System/drug effects
- Sympathetic Nervous System/metabolism
- Transcription Factors/chemistry
- Transcription Factors/genetics
- Transcription Factors/metabolism
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Affiliation(s)
- Florent Elefteriou
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
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35
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Felix K, Wise K, Manna S, Yamauchi K, Wilson BL, Thomas RL, Kulkarni A, Pellis NR, Ramesh GT. Altered cytokine expression in tissues of mice subjected to simulated microgravity. Mol Cell Biochem 2005; 266:79-85. [PMID: 15646029 DOI: 10.1023/b:mcbi.0000049136.55611.dd] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Space flight is known to induce microgravity-associated immune dysfunction in humans, non-human primates and rodents. To understand the mechanism underlying these defects, several studies in rodents have been conducted in a ground-based antiorthostatic suspension (AOS) model that would mimic the effects of microgravity. In all these in vivo studies that showed the effects on cytokine profiles actually investigated the ex vivo production from culturing the cells isolated from whole organism that was exposed to space flight and/or microgravity. So, the purpose of the study was to examine the in vivo expression of cytokines in mice in immunologically important tissue environments of mice that were subjected to AOS. Cytokines such as Interleukin-1beta, (IL-1beta), IL-2, IL-3, IL-6, Interferon-gamma (IFN-gamma) and Tumor Necrosis Factor-alpha (TNF-alpha) were measured by Enzyme Linked Immunosorbent Assay (ELISA) in the homogenates of spleen tissue, lymph nodes and also in serum of AOS mice and compared with that of control mice. AOS induced no change in the IL-3 levels, but IL-1beta was increased significantly whereas IL-2 levels decreased in spleen, lymph nodes and serum. IL-6 levels did not differ in spleen but were significantly increased in lymph nodes and serum of AOS mice. IFN-gamma levels in spleen did not change but showed nonsignificant reduction in lymph nodes and significant reduction in serum in response to AOS. TNF-alpha levels in spleen and serum were unchanged and increased in lymph nodes. This in vivo cytokine study confirms the earlier findings that microgravity-simulated conditions induce tissue-specific immune response.
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Affiliation(s)
- K Felix
- Molecular Neurotoxicology Laboratory, Department of Biology, Texas Southern University, Houston, TX 77004, USA
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36
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Pardo SJ, Patel MJ, Sykes MC, Platt MO, Boyd NL, Sorescu GP, Xu M, van Loon JJWA, Wang MD, Jo H. Simulated microgravity using the Random Positioning Machine inhibits differentiation and alters gene expression profiles of 2T3 preosteoblasts. Am J Physiol Cell Physiol 2005; 288:C1211-21. [PMID: 15689415 DOI: 10.1152/ajpcell.00222.2004] [Citation(s) in RCA: 104] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Exposure to microgravity causes bone loss in humans, and the underlying mechanism is thought to be at least partially due to a decrease in bone formation by osteoblasts. In the present study, we examined the hypothesis that microgravity changes osteoblast gene expression profiles, resulting in bone loss. For this study, we developed an in vitro system that simulates microgravity using the Random Positioning Machine (RPM) to study the effects of microgravity on 2T3 preosteoblast cells grown in gas-permeable culture disks. Exposure of 2T3 cells to simulated microgravity using the RPM for up to 9 days significantly inhibited alkaline phosphatase activity, recapitulating a bone loss response that occurs in real microgravity conditions without altering cell proliferation and shape. Next, we performed DNA microarray analysis to determine the gene expression profile of 2T3 cells exposed to 3 days of simulated microgravity. Among 10,000 genes examined using the microarray, 88 were downregulated and 52 were upregulated significantly more than twofold using simulated microgravity compared with the static 1-g condition. We then verified the microarray data for some of the genes relevant in bone biology using real-time PCR assays and immunoblotting. We confirmed that microgravity downregulated levels of alkaline phosphatase, runt-related transcription factor 2, osteomodulin, and parathyroid hormone receptor 1 mRNA; upregulated cathepsin K mRNA; and did not significantly affect bone morphogenic protein 4 and cystatin C protein levels. The identification of gravisensitive genes provides useful insight that may lead to further hypotheses regarding their roles in not only microgravity-induced bone loss but also the general patient population with similar pathological conditions, such as osteoporosis.
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Affiliation(s)
- Steven J Pardo
- Wallace H. Coulter Dept. of Biomedical Engineering, Georgia Institute of Technology and Emory University, 308D WMB, Atlanta, GA 30322, USA
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37
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Hancock CR, Brault JJ, Wiseman RW, Terjung RL, Meyer RA. 31P-NMR observation of free ADP during fatiguing, repetitive contractions of murine skeletal muscle lacking AK1. Am J Physiol Cell Physiol 2005; 288:C1298-304. [PMID: 15689408 DOI: 10.1152/ajpcell.00621.2004] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Metabolic control within skeletal muscle is designed to limit ADP accumulation even during conditions where ATP demand is out of balance with ATP synthesis. This is accomplished by the reactions of adenylate kinase (AK; ADP+ADP <--> AMP+ATP) and AMP deaminase (AMP+H(2)O --> NH(3)+IMP), which limit ADP accumulation under these conditions. The purpose of this study was to determine whether AK deficiency (AK(-/-)) would result in sufficient ADP accumulation to be visible using (31)P-NMRS during the high energy demands of frequent in situ tetanic contractions. To do this we examined the high-energy phosphates of the gastrocnemius muscle in the knockout mouse with AK1(-/-) and wild-type (WT) control muscle over the course of 64 rapid (2/s) isometric tetanic contractions. Near-complete depletion of phosphocreatine was apparent after 16 contractions in both groups. By approximately 40 contractions, ADP was clearly visible in AK1(-/-) muscle. This transient concentration of the NMR visible free ADP was estimated to be approximately 1.7 mM, and represents the first time free ADP has been directly measured in contracting skeletal muscle. Such an increase in free ADP is severalfold greater than previously thought to occur. This large accumulation of free ADP also represents a significant reduction in energy available from ATP, and has implications on cellular processes that depend on a high yield of energy from ATP such as calcium sequestration. Remarkably, the AK1(-/-) and WT muscles exhibited similar fatigue profiles. Our findings suggest that skeletal muscle is surprisingly tolerant to a large increase in ADP and by extension, a decline in energy from ATP.
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Affiliation(s)
- Chad R Hancock
- Medical Pharmacology and Physiology, College of Medicine, University of Missouri-Columbia, Columbia, MO, USA
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38
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Wang H, Hu B, Liu R, Wang Y. CHK1 affecting cell radiosensitivity is independent of non-homologous end joining. Cell Cycle 2005; 4:300-3. [PMID: 15655357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/01/2023] Open
Abstract
CHK1 is one of the most important checkpoint proteins in mammalian cells for responding to DNA damage. Cells defective in CHK1 are sensitive to ionizing radiation (IR). The mechanism by which CHK1 protects cells from IR-induced killing remains unclear. DNA double strand breaks (DSBs) induced by IR are critical lesions for cell survival. Two major complementary DNA DSBs repair pathways exist in mammalian cells, homologous recombination repair (HRR) and nonhomologous end joining (NHEJ). By using CHK1 kinase dead human cell lines established in our laboratory, we show here that although these human cell lines have different CHK1 activities with different sensitivities to IR-induced killing and G(2) accumulation, all these cell lines show similar inductions and rejoining rates of DNA DSBs. These results indicate that the different radiosensitivities and G(2) checkpoint responses in these cell lines are independent of NHEJ, suggesting that CHK1-regulated checkpoint facilitates HRR and therefore protects cells from IR-induced killing.
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Affiliation(s)
- Hongyan Wang
- Department of Radiation Oncology, Kimmel Cancer Center of Jefferson Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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Abstract
The crystal structure of the small conductance mechanosensitive channel (MscS) has been an invaluable tool in the search for the gating mechanism, however many functional aspects of the channel remain unsettled. Here we characterized the gating of MscS in Escherichia coli spheroplasts in a triple mutant (mscL−, mscS−, mscK−) background. We used a pressure clamp apparatus along with software developed in-lab to generate dose–response curves directly from two-channel recordings of current and pressure. In contrast to previous publications, we found that MscS exhibits essentially voltage-independent activation by tension, but at the same time strong voltage-dependent inactivation under depolarizing conditions. The MscS activation curves obtained under saturating ramps of pressure, at different voltages, gave estimates for the energy, area, and gating charge for the closed-to-open transition as 24 kT, 18 nm2, and +0.8, respectively. The character of activation and inactivation was similar in both K+ and Na+ buffers. Perhaps the most salient and intriguing property of MscS gating was a strong dependence on the rate of pressure application. Patches subjected to various pressure ramps from 2.7 to 240 mmHg/s revealed a midpoint of activation almost independent of rate. However, the resultant channel activity was dramatically lower when pressure was applied slowly, especially at depolarizing pipette voltages. It appears that MscS prefers to respond in full to abrupt stimuli but manages to ignore those applied slowly, as if the gate were connected to the tension-transmitting element via a velocity-sensitive “dashpot.” With slower ramps, channels inactivate during the passage through a narrow region of pressures below the activation midpoint. This property of “dumping” a slowly applied force may be important in environmental situations where rehydration of cells occurs gradually and release of osmolytes is not desirable. MscS often enters the inactivated state through subconducting states favored by depolarizing voltage. The inactivation rate increases exponentially with depolarization. Based on these results we propose a kinetic scheme and gating mechanism to account for the observed phenomenology in the framework of available structural information.
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Affiliation(s)
- Bradley Akitake
- Department of Biology, University of Maryland, College Park, MD 20742, USA
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Pornprasertsuk S, Duarte WR, Mochida Y, Yamauchi M. Overexpression of lysyl hydroxylase-2b leads to defective collagen fibrillogenesis and matrix mineralization. J Bone Miner Res 2005; 20:81-7. [PMID: 15619673 DOI: 10.1359/jbmr.041026] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2004] [Revised: 07/25/2004] [Accepted: 08/20/2004] [Indexed: 11/18/2022]
Abstract
UNLABELLED Several MC3T3-E1 cell-derived clones expressing higher levels of LH2b were analyzed for their abilities to form collagen fibrils and mineralization. The clones all exhibited smaller collagen fibrils and defective matrix mineralization in vitro and in vivo, indicating a critical role of LH2b-catalyzed post-translational modifications of collagen in bone matrix formation and mineralization. INTRODUCTION We have recently shown that lysyl hydroxylase (LH) 2b, through its action on the telopeptidyl lysine residues of collagen, regulates collagen cross-linking pathway in the osteoblastic cell line, MC3T3-E1. To further elucidate the roles of LH2b in bone physiology, the effects of overexpression of LH2b on collagen fibrillogenesis and matrix mineralization were investigated. MATERIALS AND METHODS Several MC3T3-E1-derived osteoblastic cell clones expressing higher levels of LH2b (S clones) and two controls (i.e., MC3T3-E1 cells and those transfected with an empty vector) were cultured. MALDI-TOF mass spectrometry was used to identify the LH2b. The collagen fibrillogenesis in the cultures was characterized by transmission electron microscopy, and the ability of these clones and cells to form mineralized matrix was analyzed by both in vitro and in vivo mineralization assays. RESULTS The diameter of collagen fibrils in the S clone cultures was markedly smaller than that of the controls. The onset of matrix mineralization in the S clones was significantly delayed, and considerably fewer mineralized nodules were formed in their cultures in comparison with the controls. When transplanted into immunodeficient mice, the S clones failed to form mineralized matrices in vivo, whereas a bone-like mineralized matrix was well formed by the controls. The diameter of the collagen fibrils and the timing/extent of matrix mineralization in vitro were inversely correlated with the level of LH2b. In vitro cell differentiation was unaffected by the LH2b overexpression. CONCLUSIONS These results indicate a critical role of LH2b catalyzed post-translational modification of collagen (i.e., telopeptidyl lysine hydroxylation and subsequent cross-linking) in collagen matrix formation and mineralization in bone.
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Affiliation(s)
- Suchaya Pornprasertsuk
- Dental Research Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7455, USA
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41
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Genetos DC, Geist DJ, Dawei L, Donahue HJ, Duncan RL. Fluid shear-induced ATP secretion mediates prostaglandin release in MC3T3-E1 osteoblasts. J Bone Miner Res 2005; 20:41-9. [PMID: 15619668 PMCID: PMC2929123 DOI: 10.1359/jbmr.041009] [Citation(s) in RCA: 191] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2004] [Revised: 07/20/2004] [Accepted: 08/11/2004] [Indexed: 02/04/2023]
Abstract
UNLABELLED ATP is rapidly released from osteoblasts in response to mechanical load. We examined the mechanisms involved in this release and established that shear-induced ATP release was mediated through vesicular fusion and was dependent on Ca2+ entry into the cell through L-type voltage-sensitive Ca2+ channels. Degradation of secreted ATP by apyrase prevented shear-induced PGE2 release. INTRODUCTION Fluid shear induces a rapid rise in intracellular calcium ([Ca2+]i) in osteoblasts that mediates many of the cellular responses associated with mechanotransduction in bone. A potential mechanism for this increase in [Ca2+]i is the activation of purinergic (P2) receptors resulting from shear-induced extracellular release of ATP. This study was designed to determine the effects of fluid shear on ATP release and the possible mechanisms associated with this release. MATERIALS AND METHODS MC3T3-E1 preosteoblasts were plated on type I collagen, allowed to proliferate to 90% confluency, and subjected to 12 dynes/cm2 laminar fluid flow using a parallel plate flow chamber. ATP release into the flow media was measured using a luciferin/luciferase assay. Inhibitors of channels, gap junctional intercellular communication (GJIC), and vesicular formation were added before shear and maintained in the flow medium for the duration of the experiment. RESULTS AND CONCLUSIONS Fluid shear produced a transient increase in ATP release compared with static MC3T3-E1 cells (59.8 +/- 15.7 versus 6.2 +/- 1.8 nM, respectively), peaking within 1 minute of onset. Inhibition of calcium entry through the L-type voltage-sensitive Ca2+ channel (L-VSCC) with nifedipine or verapamil significantly attenuated shear-induced ATP release. Channel inhibition had no effect on basal ATP release in static cells. Ca(2+)-dependent ATP release in response to shear seemed to result from vesicular release and not through gap hemichannels. Vesicle disruption with N-ethylmaleimide, brefeldin A, or monensin prevented increases in flow-induced ATP release, whereas inhibition of gap hemichannels with either 18alpha-glycyrrhetinic acid or 18beta-glycyrrhetinic acid did not. Degradation of extracellular ATP with apyrase prevented shear-induced increases in prostaglandin E2 (PGE2) release. These data suggest a time line of mechanotransduction wherein fluid shear activates L-VSCCs to promote Ca2+ entry that, in turn, stimulates vesicular ATP release. Furthermore, these data suggest that P2 receptor activation by secreted ATP mediates flow-induced prostaglandin release.
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Affiliation(s)
- Damian C. Genetos
- Departments of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, PA, USA
| | - Derik J. Geist
- Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Liu Dawei
- Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Henry J. Donahue
- Departments of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, PA, USA
- Orthopaedics and Rehabilitation, Pennsylvania State University College of Medicine, Hershey, PA, USA
| | - Randall L. Duncan
- Department of Orthopaedic Surgery, Indiana University School of Medicine, Indianapolis, IN, USA
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Abstract
Missions to Mars will subject living specimens to a range of low gravity environments. Deleterious biological effects of prolonged exposure to Martian gravity (0.38 g), Lunar gravity (0.17 g), and microgravity are expected, but the mechanisms involved and potential for remedies are unknown. We are proposing the development of a facility that provides a simulated Martian and Lunar gravity environment for experiments on biological systems in a well controlled laboratory setting. The magnetic adjustable gravity simulator will employ intense, inhomogeneous magnetic fields to exert magnetic body forces on a specimen that oppose the body force of gravity. By adjusting the magnetic field, it is possible to continuously adjust the total body force acting on a specimen. The simulator system considered consists of a superconducting solenoid with a room temperature bore sufficiently large to accommodate small whole organisms, cell cultures, and gravity sensitive bio-molecular solutions. It will have good optical access so that the organisms can be viewed in situ. This facility will be valuable for experimental observations and public demonstrations of systems in simulated reduced gravity.
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Affiliation(s)
- J M Valles
- Department of Physics, Brown University, Providence, RI 02912, USA.
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D'Elia R, Allen PL, Johanson K, Nickerson CA, Hammond TG. Homozygous diploid deletion strains of Saccharomyces cerevisiae that determine lag phase and dehydration tolerance. Appl Microbiol Biotechnol 2004; 67:816-26. [PMID: 15968571 DOI: 10.1007/s00253-004-1793-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2004] [Revised: 09/23/2004] [Accepted: 10/04/2004] [Indexed: 10/26/2022]
Abstract
This study identifies genes that determine length of lag phase, using the model eukaryotic organism, Saccharomyces cerevisiae. We report growth of a yeast deletion series following variations in the lag phase induced by variable storage times after drying-down yeast on filters. Using a homozygous diploid deletion pool, lag times ranging from 0 h to 90 h were associated with increased drop-out of mitochondrial genes and increased survival of nuclear genes. Simple linear regression (R2 analysis) shows that there are over 500 genes for which > 70% of the variation can be explained by lag alone. In the genes with a positive correlation, such that the gene abundance increases with lag and hence the deletion strain is suitable for survival during prolonged storage, there is a strong predominance of nucleonic genes. In the genes with a negative correlation, such that the gene abundance decreases with lag and hence the strain may be critical for getting yeast out of the lag phase, there is a strong predominance of glycoproteins and transmembrane proteins. This study identifies yeast deletion strains with survival advantage on prolonged storage and amplifies our understanding of the genes critical for getting out of the lag phase.
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Affiliation(s)
- Riccardo D'Elia
- Nephrology Section SL-45, Department of Medicine, Tulane University School of Medicine, 1430 Tulane Avenue, New Orleans, LA 70112, USA
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Abstract
Studies of mechanotransduction mediated by stress-sensitive ion channels generally focus on the site of force application to the cell. Here we show that global, cell-wide changes in cytoskeletal structure and mechanics can regulate mechanotransduction previously shown to be triggered by activation of the mechanosensitive calcium channel, polycystin-2, in the apical primary cilium of renal epithelial cells [S.M. Nauli, F.J. Alenghat, Y. Luo, E. Williams, P. Vassilev, X. Li, A.E. Elia, W. Lu, E.M. Brown, S.J. Quinn, D.E. Ingber, J. Zhou, Polycystins 1 and 2 mediate mechanosensation in the primary cilium of kidney cells. Nat. Genet. 33 (2003) 129-37]. Disrupting cytoplasmic microfilaments or microtubules in these cells eliminated fluid shear stress-induced increase of intracellular calcium. Altering the cytoskeletal force balance by inhibiting actomyosin-based tension generation (using 2,3-butanedione monoxime), interfering with microtubule polymerization (using nocodazole, cochicine, or taxol), or disrupting basal integrin-dependent extracellular matrix adhesions (using soluble GRGDSP peptide or anti-beta1 integrin antibody), also inhibited the calcium spike in response to fluid stress. These data indicate that although fluid stress-induced displacement of the primary cilium may be transduced into a calcium spike through activation of polycystin-2 and associated calcium-induced calcium release from intracellular stores, this mechanotransduction response is governed by global mechanical cues, including isometric tension (prestress) within the entire cytoskeleton and intact adhesions to extracellular matrix.
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Affiliation(s)
- Francis J Alenghat
- Vascular Biology Program, Departments of Pathology and Surgery, Children's Hospital, Harvard Medical School, Boston, MA 02115, USA
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Jiao S, Hilaire E, Guikema JA. Identification and differential accumulation of two isoforms of the CF1-beta subunit under high light stress in Brassica rapa. Plant Physiol Biochem 2004; 42:883-90. [PMID: 15694282 DOI: 10.1016/j.plaphy.2004.11.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2004] [Accepted: 11/09/2004] [Indexed: 05/01/2023]
Abstract
The chloroplast ATP synthase coupling factor CF1 complex contains five nonidentical subunits, alpha, beta, gamma, delta, and epsilon, with a stoichiometry of 3:3:1:1:1. The beta subunit contains the catalytic site for ATP synthesis during photooxidative phosphorylation in the chloroplast. In this study, we have identified two isoforms of the CF1-beta subunit at 56 and 54 kDa in the chloroplast of Brassica rapa, through isolation/purification, proteolytic digestion and internal peptide sequencing. Examining their accumulation pattern demonstrates that both isoforms coexist during chloroplast biogenesis and in mature thylakoid membranes, but the 54 kDa isoform is more apparently upregulated by light or under light stress. LiDS-PAGE shows that the 56 kDa is a major isoform of the CF1-beta subunit under normal light conditions, and its amount was not influenced during high light or other light stress treatments. The 54 kDa isoform is a minor band at normal conditions; however, it significantly increased under excess light stresses, such as high or low light with drought and/or high temperature. Particularly, a ninefold increase was observed after 8-10 h of high light treatment with drought and high temperature. The results suggest that light stress induction of the 54 kDa CF1-beta isoform may present a positive response during chloroplast photoacclimation.
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Affiliation(s)
- Shunxing Jiao
- Division of Biology, Ackert Hall, Kansas State University, Manhattan, KS 66506-4901, USA
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46
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Abstract
Major physiological changes which occur during spaceflight include bone loss, muscle atrophy, cardiovascular and immune response alterations. When trying to determine the reason why bone loss occurs during spaceflight, one must remember that all these other changes in physiology and metabolism may also have impact on the skeletal system. For bone, however, the role of normal weight bearing is a major concern and we have found no adequate substitute for weight bearing which can prevent bone loss. During the study of this problem, we have learned a great deal about bone physiology and increased our knowledge about how normal bone is formed and maintained. Presently, we do not have adequate ground based models which can mimic the tissue loss that occurs in spaceflight but this condition closely resembles the bone loss seen with osteoporosis. Although a normal bone structure will respond to application of mechanical force and weight bearing by forming new bone, a weakened osteoporotic bone may have a tendency to fracture. The study of the skeletal system during weightless conditions will eventually produce preventative measures and form a basis for protecting the crew during long term space flight. The added benefit from these studies will be methods to treat bone loss conditions which occur here on earth.
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Affiliation(s)
- St B Doty
- Hospital for Special Surgery, New York, NY 10021, USA
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Stolc V, Gauhar Z, Mason C, Halasz G, van Batenburg MF, Rifkin SA, Hua S, Herreman T, Tongprasit W, Barbano PE, Bussemaker HJ, White KP. A gene expression map for the euchromatic genome of Drosophila melanogaster. Science 2004; 306:655-60. [PMID: 15499012 DOI: 10.1126/science.1101312] [Citation(s) in RCA: 236] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
We used a maskless photolithography method to produce DNA oligonucleotide microarrays with unique probe sequences tiled throughout the genome of Drosophila melanogaster and across predicted splice junctions. RNA expression of protein coding and nonprotein coding sequences was determined for each major stage of the life cycle, including adult males and females. We detected transcriptional activity for 93% of annotated genes and RNA expression for 41% of the probes in intronic and intergenic sequences. Comparison to genome-wide RNA interference data and to gene annotations revealed distinguishable levels of expression for different classes of genes and higher levels of expression for genes with essential cellular functions. Differential splicing was observed in about 40% of predicted genes, and 5440 previously unknown splice forms were detected. Genes within conserved regions of synteny with D. pseudoobscura had highly correlated expression; these regions ranged in length from 10 to 900 kilobase pairs. The expressed intergenic and intronic sequences are more likely to be evolutionarily conserved than nonexpressed ones, and about 15% of them appear to be developmentally regulated. Our results provide a draft expression map for the entire nonrepetitive genome, which reveals a much more extensive and diverse set of expressed sequences than was previously predicted.
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Affiliation(s)
- Viktor Stolc
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, CT 06520, USA
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Abstract
The dynamics of confined water in capillaries and nanotubes suggests that gating of ion channels may involve not only changes of the pore geometry, but also transitions between water-filled and empty states in certain locations. The recently solved heptameric structure of the small mechanosensitive channel of Escherichia coli, MscS, has revealed a relatively wide (7-15 A) yet highly hydrophobic transmembrane pore. Continuum estimations based on the properties of pore surface suggest low conductance and a thermodynamic possibility of dewetting. To test the predictions we performed molecular dynamics simulations of MscS filled with flexible TIP3P water. Irrespective to the initial conditions, several independent 6-ns simulations converged to the same stable state with the pore water-filled in the wider part, but predominantly empty in the narrow hydrophobic part, displaying intermittent vapor-liquid transitions. The polar gain-of-function substitution L109S in the constriction resulted in a stable hydration of the entire pore. Steered passages of Cl(-) ions through the narrow part of the pore consistently produced partial ion dehydration and required a force of 200-400 pN to overcome an estimated barrier of 10-20 kcal/mole, implying negligibly low conductance. We conclude that the crystal structure of MscS does not represent an open state. We infer that MscS gate, which is similar to that of the nicotinic ACh receptor, involves a vapor-lock mechanism where limited changes of geometry or surface polarity can locally switch the regime between water-filled (conducting) and empty (nonconducting) states.
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Affiliation(s)
- Andriy Anishkin
- Biology Department, University of Maryland, College Park, Maryland, USA
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49
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Chiang CS, Anishkin A, Sukharev S. Gating of the large mechanosensitive channel in situ: estimation of the spatial scale of the transition from channel population responses. Biophys J 2004; 86:2846-61. [PMID: 15111402 PMCID: PMC1304154 DOI: 10.1016/s0006-3495(04)74337-4] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Physical expansion associated with the opening of a tension-sensitive channel has the same meaning as gating charge for a voltage-gated channel. Despite increasing evidence for the open-state conformation of MscL, the energetic description of its complex gating remains incomplete. The previously estimated in-plane expansion of MscL is considerably smaller than predicted by molecular models. To resolve this discrepancy, we conducted a systematic study of currents and dose-response curves for wild-type MscL in Escherichia coli giant spheroplasts. Using the all-point histogram method and calibrating tension against the threshold for the small mechanosensitive channel (MscS) in each patch, we found that the distribution of channels among the subconducting states is significantly less dependent on tension than the distribution between the closed and conducting states. At -20 mV, all substates together occupy approximately 30% of the open time and reduce the mean integral current by approximately 6%, essentially independent of tension or P(o). This is consistent with the gating scheme in which the major rate-limiting step is the transition between the closed state and a low-conducting substate, and validates both the use of the integral current as a measure of P(o), and treatment of dose-response curves in the two-state approximation. The apparent energy and area differences between the states deltaE and deltaA, extracted from 29 independent dose-response curves, varied in a linearly correlated manner whereas the midpoint tension stayed at approximately 10.4 mN/m. Statistical modeling suggests slight variability of gating parameters among channels in each patch, causing a strong reduction and correlated spread of apparent deltaE and deltaA. The slope of initial parts of activation curves, with a few channels being active, gave estimates of deltaE = 51 +/- 13 kT and deltaA = 20.4 +/- 4.8 nm(2), the latter being consistent with structural models of MscL, which predict deltaA = 23 nm(2).
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Affiliation(s)
- Chien-Sung Chiang
- Department of Biology, University of Maryland College Park, Maryland 20742, USA
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50
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Abstract
Nucleus movement is essential during nucleus positioning for tissue growth and development in eukaryotic cells. However, molecular regulators of nucleus movement in interphase fibroblasts have yet to be identified. Here, we report that nuclei of Swiss 3T3 fibroblasts undergo enhanced movement when subjected to shear flows. Such movement includes both rotation and translocation and is dependent on microtubule, not F-actin, structure. Through inactivation of Rho GTPases, well-known mediators of cytoskeleton reorganization, we demonstrate that Cdc42, not RhoA or Rac1, controls the extent of nucleus translocation, and more importantly, of nucleus rotation in the cytoplasm. In addition to generating nuclei movement, we find that shear flows also causes repositioning of the MTOC in the direction of flow. This behavior is also controlled by Cdc42 via the Par6/protein kinase Czeta pathway. These results are the first to establish Cdc42 as a molecular regulator of not only shear-induced MTOC polarization in Swiss 3T3 fibroblasts, but also of shear-induced microtubule-dependent nucleus movement. We propose that the movements of MTOC and nucleus are coupled chemically, because they are both regulated by Cdc42 and dependent on microtubule structure, and physically, possibly via Hook/SUN family homologues similar to those found in Caenorhabditis elegans.
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Affiliation(s)
- Jerry S H Lee
- Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, MD 21218, USA
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