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Müller GA, Ussar S, Tschöp MH, Müller TD. Age-dependent membrane release and degradation of full-length glycosylphosphatidylinositol-anchored proteins in rats. Mech Ageing Dev 2020; 190:111307. [PMID: 32628941 DOI: 10.1016/j.mad.2020.111307] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 06/18/2020] [Accepted: 06/29/2020] [Indexed: 01/28/2023]
Abstract
Glycosylphosphatidylinositol (GPI)-anchored proteins (GPI-APs) are associated with the surface of eucaryotic cells only through a covalently coupled carboxy-terminal GPI glycolipid structure which is anchored at the outer leaflet of plasma membranes. This mode of membrane association may be responsible for the recent observations that full-length GPI-APs harbouring the complete GPI anchor are (i) released from isolated rat adipocytes in vitro and (ii) expressed in rat and human serum. The upregulation of the adipocyte release in response to increased cell size and blood glucose/insulin levels of the donor rats and downregulation of the expression in serum of insulin resistant and diabetic rats have been reconciled with enhanced degradation of the full-length GPI-APs released into micelle-like complexes together with (lyso) phospholipids and cholesterol by serum GPI-specific phospholipase D (GPI-PLD). Here by using a sensitive and reliable sensing method for full-length GPI-APs, which relies on surface acoustic waves propagating over microfluidic chips, the upregulation of (i) the release of the full-length GPI-APs CD73, alkaline phosphatase and CD55 from isolated adipocyte plasma membranes monitored in a "lab-on-the-chip" configuration, (ii) their release from isolated rat adipocytes into the incubation medium and (iii) the lipolytic cleavage of their GPI anchors in serum was demonstrated to increase with age (3-16 weeks) and body weight (87-477 g) of (healthy) donor rats. In contrast, the amount of full-length GPI-APs in rat serum, as determined by chip-based sensing, turned out to decline with age/body weight. These correlations suggest that age-/weight-induced alterations (in certain biophysical/biochemical characteristics) of plasma membranes are responsible for the release of full-length GPI-APs which becomes counteracted by elevated GPI-PLD activity in serum. Thus, sensitive and specific measurement of these GPI-AP-relevant parameters may be useful for monitoring of age-related cell surface changes, in general, and diseases, in particular.
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Affiliation(s)
- Günter A Müller
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center (HDC) at Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Oberschleissheim, Germany; German Center for Diabetes Research (DZD), Oberschleissheim, Germany; Department Biology I, Genetics, Ludwig-Maximilians-Universität München, Planegg, Martinsried, Germany.
| | - Siegfried Ussar
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center (HDC) at Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Oberschleissheim, Germany; German Center for Diabetes Research (DZD), Oberschleissheim, Germany; Division of Metabolic Diseases, Department of Medicine, Technische Universität München, München, Germany
| | - Matthias H Tschöp
- German Center for Diabetes Research (DZD), Oberschleissheim, Germany; Division of Metabolic Diseases, Department of Medicine, Technische Universität München, München, Germany; Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Oberschleissheim, Germany
| | - Timo D Müller
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center (HDC) at Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Oberschleissheim, Germany; German Center for Diabetes Research (DZD), Oberschleissheim, Germany; Department of Pharmacology and Experimental Therapy, Institute of Experimental and Clinical Pharmacology and Toxicology, Eberhard Karls University Hospitals and Clinics, Tübingen, Germany
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Bejarano E, Murray JW, Wang X, Pampliega O, Yin D, Patel B, Yuste A, Wolkoff AW, Cuervo AM. Defective recruitment of motor proteins to autophagic compartments contributes to autophagic failure in aging. Aging Cell 2018; 17:e12777. [PMID: 29845728 PMCID: PMC6052466 DOI: 10.1111/acel.12777] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/28/2018] [Indexed: 12/11/2022] Open
Abstract
Inability to preserve proteostasis with age contributes to the gradual loss of function that characterizes old organisms. Defective autophagy, a component of the proteostasis network for delivery and degradation of intracellular materials in lysosomes, has been described in multiple old organisms, while a robust autophagy response has been linked to longevity. The molecular mechanisms responsible for defective autophagic function with age remain, for the most part, poorly characterized. In this work, we have identified differences between young and old cells in the intracellular trafficking of the vesicular compartments that participate in autophagy. Failure to reposition autophagosomes and lysosomes toward the perinuclear region with age reduces the efficiency of their fusion and the subsequent degradation of the sequestered cargo. Hepatocytes from old mice display lower association of two microtubule-based minus-end-directed motor proteins, the well-characterized dynein, and the less-studied KIFC3, with autophagosomes and lysosomes, respectively. Using genetic approaches to mimic the lower levels of KIFC3 observed in old cells, we confirmed that reduced content of this motor protein in fibroblasts leads to failed lysosomal repositioning and diminished autophagic flux. Our study connects defects in intracellular trafficking with insufficient autophagy in old organisms and identifies motor proteins as a novel target for future interventions aiming at correcting autophagic activity with anti-aging purposes.
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Affiliation(s)
- Eloy Bejarano
- Department of Developmental and Molecular Biology; Albert Einstein College of Medicine; Bronx New York
- Institute for Aging Studies; Albert Einstein College of Medicine; Bronx New York
| | - John W. Murray
- Marion Bessin Liver Research Center; Albert Einstein College of Medicine; Bronx New York
- Department of Anatomy and Structural Biology; Albert Einstein College of Medicine; Bronx New York
| | - Xintao Wang
- Marion Bessin Liver Research Center; Albert Einstein College of Medicine; Bronx New York
- Department of Anatomy and Structural Biology; Albert Einstein College of Medicine; Bronx New York
| | - Olatz Pampliega
- Institut des Maladies Neurodégénératives UMR5293; Universite de Bordeaux; Bordeaux France
- CNRS; Institut des Maladies Neurodégénératives; UMR 5293 C Bordeaux Cedex France
| | - David Yin
- Marion Bessin Liver Research Center; Albert Einstein College of Medicine; Bronx New York
| | - Bindi Patel
- Department of Developmental and Molecular Biology; Albert Einstein College of Medicine; Bronx New York
- Institute for Aging Studies; Albert Einstein College of Medicine; Bronx New York
| | - Andrea Yuste
- Department of Developmental and Molecular Biology; Albert Einstein College of Medicine; Bronx New York
- Institute for Aging Studies; Albert Einstein College of Medicine; Bronx New York
| | - Allan W. Wolkoff
- Marion Bessin Liver Research Center; Albert Einstein College of Medicine; Bronx New York
- Department of Anatomy and Structural Biology; Albert Einstein College of Medicine; Bronx New York
- Division of Hepatology, Albert Einstein College of Medicine and; Montefiore Medical Center; Bronx New York
| | - Ana Maria Cuervo
- Department of Developmental and Molecular Biology; Albert Einstein College of Medicine; Bronx New York
- Institute for Aging Studies; Albert Einstein College of Medicine; Bronx New York
- Marion Bessin Liver Research Center; Albert Einstein College of Medicine; Bronx New York
- Department of Anatomy and Structural Biology; Albert Einstein College of Medicine; Bronx New York
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Lustyik G. Photobleaching measurements of diffusion in cell membranes and aqueous cell compartments. CURRENT PROTOCOLS IN CYTOMETRY 2008; Chapter 2:Unit 2.12. [PMID: 18770695 DOI: 10.1002/0471142956.cy0212s16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
This commentary unit discusses in great detail the theoretical nature of fluorescence recovery after photobleaching (FRAP). This information is crucial to an understanding of how and why FRAP works in a cell system. Further, understanding how to interpret the data sets requires a sound knowledge of the processes involved. Of primary importance are the nature of membrane diffusion and the nature of the multiple compartments into which fluorescent dyes can enter. The unit provides a complete discussion of all aspects of FRAP from the perspective of cellular measurements.
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Affiliation(s)
- G Lustyik
- University of Pécs, Faculty of Medicine, Pécs, Hungary
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Kitani K. What really declines with age? The Hayflick Lecture for 2006 35th American Aging Association. AGE (DORDRECHT, NETHERLANDS) 2007; 29:1-14. [PMID: 19424826 PMCID: PMC2267679 DOI: 10.1007/s11357-006-9014-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2006] [Revised: 08/25/2006] [Accepted: 08/28/2006] [Indexed: 05/11/2023]
Abstract
In order to understand the basic mechanisms underlying the organismic aging process, considerable efforts have been devoted in the last half-century to biochemical (enzyme activity) alterations in specific tissues and organs of various organisms associated with aging. When a decline in enzyme activities with age has been found in a study, especially for key enzymes such as antioxidant enzymes, the results have often been interpreted as a cause for the aging of the entire body. Retrospectively, however, these changes turned out to be so variable--depending on species, strains and sexes of animals--that the interpretation of these results in general terms of aging became invalid. Further, unlike the prediction for the whole human body, many enzyme activities in a vital organ, such as the liver, remained unchanged, as long as the old subjects remained healthy. However, enzyme activities in old animals and humans are often more susceptible to morbidities and frailties, which themselves are often accompanied by infections and malnutrition. Despite the rather stable enzyme functions in the liver with age, a distinct and progressive decline in the lateral diffusion coefficient of proteins of hepatocyte plasma membranes has been demonstrated by fluorescence recovery after photobleaching (FRAP), which was implicated as the cause for the decline of hepatocyte functions such as ouabain (and taurocholate) hepatic uptake and their eventual biliary excretion. Since a similar decline in protein diffusion coefficients was observed in brain and muscle cells, it is likely that these changes are occurring in common with many cell types of the body, thus causing a delay in transmembrane transport of endogenous and exogenous substances whose transports are mediated by membrane proteins. In attempts to prolong the life spans of animals other than by calorie restriction, but instead using deprenyl or tetrahydrocurcumin, works by the author and coworkers are introduced and discussed. Despite limited success along these lines thus far, further attempts are encouraged, primarily to understand the mechanisms underlying organismic aging processes and to find a practical way to prolong the health span of the elderly.
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Affiliation(s)
- Kenichi Kitani
- National Institute for Longevity Sciences, 36-3, Gengo, Morioka-cho, Obu-shi Aichi, 474-8522, Japan.
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Kitani K. "My involvement in aging research was just a series of coincidences" An interview with Kenichi Kitani. Interview by Sataro Goto. Biogerontology 2006; 6:211-21. [PMID: 16041625 DOI: 10.1007/s10522-005-7949-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2004] [Accepted: 02/28/2005] [Indexed: 10/25/2022]
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Megli FM, Sabatini K. Mitochondrial phospholipid bilayer structure is ruined after liver oxidative injury in vivo. FEBS Lett 2004; 573:68-72. [PMID: 15327977 DOI: 10.1016/j.febslet.2004.07.057] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2004] [Accepted: 07/19/2004] [Indexed: 01/21/2023]
Abstract
The purpose of this study was to investigate whether, after oxidative injury in vivo, liver mitochondrial phospholipids suffered from structural defects similar to those we have previously observed after either chemical oxidation or respiration state IV incubation of isolated mitochondria in vitro. Oxidative injury of the liver was simulated by endogastric administration of CCl4 to rats in variable amounts for different times, under various conditions. Measurements of the phospholipid bilayer packing order were carried out by electron paramagnetic resonance (EPR) spectrometry of oriented planar samples of phospholipids extracted from liver mitochondria, spin labeled with 5-doxylstearoyl-lecithin. Disordering of the bilayer was revealed by the anisotropy loss of EPR spectra and reached a maximum value 4.5 h after CCl4 administration, vanishing thereafter. The observed disorder also increased with the amount of CCl4 administered, showing distinct dose-dependence, while administration of resveratrol soon after carbon tetrachloride decreased bilayer disordering by 50%. On the contrary, the order parameter S of spin labeled lecithin in isolated mitochondrial membranes from intoxicated rats revealed no change in membrane fluidity after oxidative stress. It is concluded that the phospholipid damage leading to disturbed bilayer geometry after oxidative attack already observed in model membranes and in isolated mitochondria in vitro also occurs in a simulated pathological state in vivo, indicating its possible occurrence also in real oxidative stress-linked pathologies as a contribution to the onset/sustaining of related diseases.
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Affiliation(s)
- Francesco M Megli
- Dipartimento di Biochimica e Biologia Molecolare, Università di Bari, Centro di Studio sui Mitocondri e Metabolismo Energetico--CNR, Via E. Orabona, 4-70126 Bari, Italy.
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Larbi A, Douziech N, Khalil A, Dupuis G, Gheraïri S, Guérard KP, Fülöp T. Effects of methyl-β-cyclodextrin on T lymphocytes lipid rafts with aging. Exp Gerontol 2004; 39:551-8. [PMID: 15050290 DOI: 10.1016/j.exger.2003.10.031] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2003] [Revised: 09/07/2003] [Accepted: 10/09/2003] [Indexed: 02/06/2023]
Abstract
Aging is associated with a decline in immune functions. Among them, T-cell activation is altered at several points of the signaling cascade following TCR engagement. Recent findings suggest that lipid rafts act as a platform in the initiation of T-cell activation. We have previously demonstrated that cholesterol content in T-cells increased with aging, especially in lipid rafts. Cholesterol, which is a major component of lipid rafts, serves to stabilize their structure. We hypothesized that restoring T-cell cholesterol content and membrane fluidity would restore, at least in part, T-cell function via lipid rafts. We measured the lipid rafts coalescence, the p56(Lck) and linker of activated T-cell (LAT) signaling molecules recruitment and activation, the cholesterol content and fluidity in T-cell membrane after different methyl-beta-cyclodextrin (MBCD) treatments. Our results show that high concentration of MBCD (10 mM) completely disorganized the lipid rafts in T-cell membranes of young and elderly donors, however, T-cells from elderly donors were less sensitive than T-cells of young donors to low concentration of MBCD (0.5 mM). p56(Lck) and LAT recruitment and activation were affected in T-cells of both aged groups. MBCD treatment did not affect the cholesterol content and fluidity of T-cell membranes of young donors, while the cholesterol content was decreased and fluidity increased in lipid rafts of elderly donors. These results suggested that cholesterol extraction by MBCD increased the fluidity and disrupted lipid rafts organization. The increase in cholesterol content in lipid rafts with aging and its decrease by biochemical extraction were able to affect early signaling molecules activation. Restoring cholesterol content and fluidity may have beneficial effects, however, MBCD disorganized the membrane and this might not completely restore the T-cell activation via lipid rafts with aging. Altogether these results suggest that defects in cholesterol cellular homeostasis may be part of T-cell immunosenescence via lipid rafts dysfunction.
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Affiliation(s)
- Anis Larbi
- Research Center on Aging, Sherbrooke Geriatric University Institute, University of Sherbrooke, Sherbrooke, Que., Canada J1H 5N4
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Larbi A, Douziech N, Dupuis G, Khalil A, Pelletier H, Guerard KP, Fülöp T. Age-associated alterations in the recruitment of signal-transduction proteins to lipid rafts in human T lymphocytes. J Leukoc Biol 2003; 75:373-81. [PMID: 14657209 DOI: 10.1189/jlb.0703319] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Aging is associated with a decline in T cell activation and proliferation, but the underlying mechanisms are not fully understood. Recent findings suggest that lipid rafts act as a platform in the initiation of T cell activation by selectively recruiting signaling proteins associated with formation of the initial complex of signal transduction. We tested the hypothesis that lipid raft properties are altered in T lymphocytes from elderly, healthy individuals in comparison with young subjects. Results showed that the cholesterol content of lipid rafts derived from these cells was consistently higher in the case of elderly donors and that membrane fluidity was decreased. In addition, lipid rafts coalescence to the site of T cell receptor engagement was impaired in T cells from elderly donors. The recruitment of p56(lck), linker of activated T cells, and their tyrosine-phosphorylated forms to lipid rafts was decreased in activated T cells from aged individuals. CD45 was not recruited to the lipid raft fractions in either group of subjects. Our data suggest that some properties of lipid rafts are altered in aging, and this finding may be part of the causes for the decline in T cell functions that are observed in elderly individuals.
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Affiliation(s)
- Anis Larbi
- Research Center on Aging, Geriatric Institute, Clinical Research Center, University of Sherbrooke, 1036 Belvedere St. South, Sherbrooke, QC, Canada J1H 4C4
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Fülöp T, Larbi A, Dupuis G, Pawelec G. Ageing, autoimmunity and arthritis: Perturbations of TCR signal transduction pathways with ageing - a biochemical paradigm for the ageing immune system. Arthritis Res Ther 2003; 5:290-302. [PMID: 14680505 PMCID: PMC333419 DOI: 10.1186/ar1019] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2003] [Revised: 10/01/2003] [Accepted: 10/13/2003] [Indexed: 02/07/2023] Open
Abstract
It is widely accepted that cell-mediated immune functions decline with age, rendering an individual more susceptible to infection and possibly cancer, as well as to age-associated autoimmune diseases. The exact causes of T-cell functional decline are not known. One possible cause could be the development of defects in the transduction of mitogenic signals following TCR stimulation. This T-cell hyporesponsiveness due to defects of signalling through the TCR either from healthy elderly subjects or from individuals with autoimmune diseases such as rheumatoid arthritis or systemic lupus erythematosus results in an impaired ability to mount efficient immune responses and to maintain responsiveness to foreign antigens. This implies that a high proportion of autoreactive T cells might accumulate either intrathymically or in the periphery. T-cell anergy and differential TCR signalling could thus also be key players in the disruption of tolerance and the onset of autoimmune diseases. The increasing number of the elderly may lead to an increase of clinically important autoimmune diseases. We will review the signal transduction changes through the TCR-CD3 complex in T lymphocytes from healthy elderly subjects, which result in a modification of the activation of transcription factors involved in IL-2 gene expression leading to decreased IL-2 production. The putative contribution of altered T-cell signalling with ageing in the development of autoimmune diseases will be also discussed.
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Affiliation(s)
- Tamàs Fülöp
- Research Center on Ageing, Sherbrooke Geriatric University Institute, University of Sherbrooke, Quebec, Canada.
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Zs-Nagy I. The biological waste product formation in the light of the membrane hypothesis of aging. Arch Gerontol Geriatr 2002; 34:329-41. [PMID: 14764334 DOI: 10.1016/s0167-4943(02)00010-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2001] [Revised: 12/10/2001] [Accepted: 12/18/2001] [Indexed: 12/28/2022]
Abstract
The membrane hypothesis of aging (MHA) explains the biological waste product (lipofuscin) formation as a disbalance between the rates of protein synthesis and damage, as well as of elimination of the damaged components. Although, this concept has not been refuted on the basis of any experimental evidence, it has neither been widely accepted. During the last decade the general interest has turned toward the molecular genetics so intensely, that research aimed at clarifying cell biological mechanisms became so to say hibernated. Nowadays it is being recognized more and more that after the complete description of the human genetic code, attention has to be dedicated again to the cellular mechanisms explaining the function of the gene products (proteins). In this context, our experimental findings described during the recent years may become again the subject of interest. We have shown that the in vivo inhibition of the lysosomal thiol-proteinase functions by sublethal doses of leupeptin in young, adult and old mice results in a considerable increase (about 30%) of the immobile fraction of membrane proteins in hepatocyte plasma membrane, meanwhile the lateral diffusion constant of the still mobile membrane proteins increased. These observations were interpreted as signs of a general slowing down of protein turnover in the plasma membrane, just by inhibiting the elimination mechanisms in the lysosomes. This paper will discuss the theoretical conclusions and significance of these findings for the biological waste product formation, as a basic cell biological function.
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Affiliation(s)
- Imre Zs-Nagy
- Department of Gerontology (VILEG, Hungarian Section), University of Debrecen, Medical and Health Science Center, PO Box 50, Debrecen H-4012, Hungary.
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Zs-Nagy I. Enzyme activities in the light of the membrane hypothesis of aging. [An answer to K. Kitani, Mech. Ageing Dev. 107 (1999), 299-322]. Mech Ageing Dev 2001; 122:811-21. [PMID: 11337010 DOI: 10.1016/s0047-6374(01)00237-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The paper of Kitani cited in the title has raised an apparent contradiction regarding the validity of certain aspects of the membrane hypothesis of aging (MHA). He collected data showing that a number of detoxifying liver enzyme activities, although decline with age in male Fischer 344 rats, remain at an unchanged level in females of the same strain. He concluded that the main assumption of the MHA, according to which intracellular enzyme activities generally decline with age, cannot be maintained, and invoked me (p. 312) 'ellipsis to provide in the future ample (and convincing) evidence' in this respect. The present paper answers this criticism by showing that the apparent contradiction mentioned above is based on a misunderstanding on behalf of Kitani. Namely, MHA speaks about the general, density-dependent decline of the catalytic rate constant of any enzyme (k(cat)), i.e., activity per mole of enzyme, being the true specific activity of the enzymes. This parameter inevitably decreases at the increased physical density of the intracellular colloids during aging. This statement derives from the molecular enzyme kinetic models, and has extensively been proven experimentally, too. On the other hand, Kitani speaks about enzyme activities per mg total protein content of certain tissue extracts, which is a very illdefined parameter, since the concentration of the measured enzyme remains unknown. Therefore, this latter parameter is irrelevant from the point of view of MHA in any aspect.
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Affiliation(s)
- I Zs-Nagy
- Department of Gerontology (VILEG Hungarian Section), University of Debrecen, Medical Faculty, PO Box 50, Debrecen, H-4012, Hungary.
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Zs -Nagy I, Tanaka S, Kitani K. Comparison of the lateral diffusion coefficient of hepatocyte plasma membrane proteins in three strains of sensescence accelerated mouse (SAM). Arch Gerontol Geriatr 2001; 32:119-137. [PMID: 11313103 DOI: 10.1016/s0167-4943(01)00085-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The lateral diffusion coefficients of proteins (D(p)) were measured in hepatocyte plasma membrane in freshly prepared liver smears by means of the fluorescence recovery after photobleaching (FRAP) method. D(p) was measured after development of peroxide-induced autofluorescence (PIAF) in a total of 115 senescence accelerated mice (SAM), distributed in three strains, at least five age-groups in each, as follows: (i) SAMR1TA (25 males and 22 females), medium life span (MLS) in months, under specific pathogen free (SPF) conditions, MLS(spf) 20.1 and 20.0, respectively, while under conventional conditions, MLS(Deltapf)=18.9 in average for both sexes; (ii) SAMP6/Ta (18 males and 17 females), MLS(spf)=17.1 and 15.3, respectively, and MLS(cc)=8.1 for both sexes; (iii) SAMP6/Ta (17 males and 16 females), MLS(spf)=15.6 and 14.7, respectively, and MLS(cc)=10.0 for both sexes. A highly significant negative linear age-correlation of D(p) (R=0.975 or higher) was found in each strain, being roughly proportional with the MLS(cc) values. Since the studied mice kept under SPF conditions survived longer, than under conventional conditions, the actual age-dependent decay rates of D(p) values did not differ significantly in two pairs of comparisons (female R1/P6 and female R1/P8), whereas they did in all other possible pairs, including also the normal C57BL/6 mice. The main conclusion can be drawn that the D(p) of hepatocyte membranes is a good biomarker of aging and survival also in SAM, as in all other inbred and outbred rodents, studied so far.
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Affiliation(s)
- I Zs -Nagy
- National Institute for Longevity Sciences (NILS), 36-3, Gengo, Morioka-cho Obu-shi, 474-8522, Aichi, Japan
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