Post on 02-May-2015
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Adriana Maggi
DOCENTE DI BIOTECNOLOGIE FARMACOLOGICHECORSO DI LAUREA SPECIALISTICA IN
BIOTECNOLOGIE DEL FARMACO
AA 2011/2012Lezione 7
LE BASI BIOLOGICHE DELL’ INVECCHIAMENTO
Invecchiamento e genetica
Regolazione endocrina dell’invecchiamento
Invecchiamento e ambiente
Non-Programmed Passive Aging Theories
• Aging is a passive result of an organism’s inability to better resist fundamental deteriorative processes.
• Aging serves no purpose, is not an adaptation, is not programmed.• Compatible with traditional evolutionary mechanics theory. Mammals
needing more time for development needed a longer life span and therefore developed better maintenance and repair mechanisms that consequently delayed onset of age-related symptoms and diseases relative to shorter-lived mammals.
• Poor fit to many other observations of humans, other mammals, and other organisms particularly those that die suddenly from apparent biological suicide following reproduction rather than from gradual deterioration (e.g. Octopus, salmon)
Programmed Active Aging Theories
• Organisms are purposely designed and genetically programmed to age or otherwise limit life span because the deterioration and life span limitation serves an evolutionary purpose.
• Aging is an adaptation, a purposeful design feature resulting from the evolution process.
• Aging is the result of a potentially complex active aging mechanism or “life span management system.”
• The mechanism could sense external conditions in order to adapt life span to local or temporary conditions and could operate by manipulating the maintenance and repair functions.
Aging Theory Status
• “Main line” consensus of current gerontologists favors the passive theories. Earlier simple deterioration theories have little current scientific credibility in the biology community while still popular in the human-oriented (physician) community.
• Some relatively recent discoveries appear to favor aging-by-design theories.
• Efforts to explain aging based on traditional mechanics and efforts to explain other discrepancies with alternative mechanics cannot be simultaneously valid. Eventually there will be a unified theory.
“Non-Aging” Species
• Some species have been identified that apparently do not age or have negligible senescence. Older individuals do not appear to be weaker, less agile, less reproductive, more susceptible to disease, or otherwise less fit than younger animals. (Ages of some wild animals can be determined by annual marks in scales or bones similar to tree rings.)
• Some species with age of oldest recorded specimen:
Rougheye Rockfish 205 Years
Lake Sturgeon152 Years
Aldabra Tortise152 Years
• Common U.S. Eastern Box Turtle is also long-lived (~100 years).
• Non-aging species tend to defeat simple deterioration theories and suggest dramatically longer human life spans are possible.
QUALE APPROCCIO SEGUIRE PER LO STUDIO DELLE BASI MOLCOLARI DELL’INVECCHIAMENTO?
Planned Obsolescence Theory
Telomerase Theory of Aging
The Neuroendocrine Theory
The Free Radical Theory
Mitochondrial Theory of Aging
The Membrane Theory of Aging
The Hayflick Limit Theory
Glycosylation Theory of Aging
(The cell waste accumulation)
Aging Theories
Immune system alterations
MALATTIE GENETICHE ESEMPI DI INVECCHIAMENTO PRECOCE
Progeria and Werner Syndrome
• Hutchinson-Guilford Progeria, a very rare human genetic disease, accelerates many symptoms of aging including atherosclerotic heart disease. Victims usually die by age 13.
• Werner syndrome, another genetic disease, involves acceleration of most symptoms of aging including baldness, hair and skin conditions, heart disease, calcification of blood vessels, some cancers, cataracts, arthritis, diabetes, etc. Victims usually die by age 50.
• These conditions suggest aging is centrally controlled such that a single genetic defect could result in proportionally accelerating all of the expressed symptoms. Central control suggests aging-by-design
Il gene LMNA che codifica per le laminine di tipo A è stato caratterizzato nel 1993 e mappato sul cromosoma 1q21.2-q21.3 (Lin and Worman 1993; Wydner et al. 1996).
La prima malattia umana causata da mutazioni della laminina A identificata per mezzo di clonaggio posizionale era autosomica dominante e determinava la distrofia muscolare Emery-Dreifuss
• Autosomal dominant (and rarely recessive) Emery-Dreifuss muscular dystrophy
• Cardiomyopathy dilated 1A• Limb-girdle muscular dystrophy
type 1B• Congenital muscular dystrophy• “Heart-hand” syndrome• Adipose Tissue• Dunnigan-type familial partial
lipodystrophy
• Lipoatrophy with diabetes and other features of
• insulin resistance• Atypical lipodystrophy
syndromes• Mandibuloacral dysplasia• Peripheral Nerve• Charcot-Marie-Tooth disease
type 2B1• Progeria Phenotype• Hutchinson-Gilford progeria
syndrome• Atypical Werner Syndrome• Variant progeroid disorders• Mandibuloacral Dysplasi
Laminopatie
Funzioni delle laminine
Capell and Collins Nature Reviews Genetics 7, 940–952 (December 2006) | doi:10.1038/nrg1906
Lipodistrofia familiare
Charcot-Marie-Tooth
progeriaDisplasia mandibulo sacrale
Una malattia autosomica dominante e sporadica e rara che determina invecchiamento precoce: in genere il paziente muore a 13 anni circa per patologie cardiache
La base genetica per molti casi di questa patologia consiste
nella mutazione della tripletta GGC in GGT nel codone 608 della laminina A (LMNA) .
Questo determina l’insorgenza di un sito di splicing criptico porta alla sintesi di una proteina con una delezione di 50 aa. La regione deleta ha in se la sequenza riconosciuta da enzimi proteolitici che fanno maturare la Laminina. In mancanza di questa parte della proteina, questa viene carbossifarnesilata e si accumula a livello endocellulare e soprattutto a causa della farnesilazione, nella membrana nucleare.
Hutchinson-Gilford progeria syndrome
Figure 1. Processing of lamin A in normal and HGPS cells
Meshorer E., Gruenbaum Y. J. Cell Biol. 2008:181:9-13
Invecchiamento e genetica
La presenza di laminina mutata (progerin)altera le funzione della membrana nucleare, la sua permeabilità e la trascrizione genica.
The is a mouse model of progeria where the prelamin A is not mutated. Instead, the metallopeptidase ZMPSTE24, the specific protease that is required to remove the C-terminus of prelamin A, is missing.
INVECCHIAMENTO E PROGERIE
I malati di progerie non mostrano:
deficit cognitivielevati livelli ematici di colesterolo e LDLelevati livelli di prot C reattiva
Che generalmente si accompagnano all’invecchiamento
SINDROME DI WERNER
I portatori di mutazioni che dterminano la sindrome di Werner manifestano molto precocemente:cataratta, arteriosclerosi, osteoporosi, diabete mellito di tipo II, tumori di origine mesenchimale.Generalmente la causa di morte è infarto o tumori.
Sindrome di WernerUna patologia autosomica recessiva
La mutazione genica è a carico della DNA elicasi (cromosoma 8
braccio corto) che accorcia la lunghezza dei telomeri.
La malattia si manifesta alla pubertà e i portatori della
mutazione vivono fino circa 40 anni di età.
A. Topo I usually found in eukaryotes binds the 3’ end of the broken DNA strand, and removes (+) or (-) supercoils. As replicating DNA moves through the structure, the two parental strands (black) are separated by the helicase, while positive supercoiling is removed by the 3’ topoisomerase.
B. A machine able to separate the daughtermolecules at the end of replication is formed by a helicase (red) removing the last turns of parental DNA and a type II topoisomerase(green) untangling the daughter duplexes.
C. Nucleosome disruption.
The positive supercoiling produced by the translocating helicase H (red) destabilizes the nucleosome, while a topoisomerase T (5’ or 3’ Topo I,or eukaryotic topo II, green) efficiently relaxes the negative supercoiling, reforming the normal duplex behind the helicase.
MAPPA DELLE MUTAZIONI IN PAZIENTI CON MALATTIA DI WERNER
HRDC: Human Hematopoietic Cell Derived Rna Cyclase
Le proteine che interagiscono direttamente con la RecQ elicasi comprendono:Ku70/80, BLM, FEN1, TRF2, p53, polß, polδ, RAD51, RAD52, RAD54B, RPA, POT1, PCNA, PARP1, MRE11, e Cdc5L
coinvolte in:
Replicazione del DNA, Riparazione del DNA,RicombinazioneMetabolismo dei telomeri
Telomero = una regione di DNA ripetitivo al termine del cromosoma necessario per proteggere la parte terminale del cromosoma stesso nei confronti di enzimi degradativi o fusioni con cromosomi vicini.
telos (τέλος) “fine“ merοs (μέρος, root: μερ-) "parte".
Con la replicazione dei cromosomi il terminale dei cromosomi si erode e la parte del telomero si accorcia. Un telomero in una cella giovane puo’ raggiungere le 15000 paia di basi (ogni divisione si raccorcia di 25-200 pb)
double stranded, a G-rich single strand forms a terminal 3' overhang
Telomeric repeat-binding factor 1
prote
ction
of te
lomere
s
Telomerase is a ribonucleoprotein polymerase that maintains telmere ends by addition of the telomere repeat
TTAGGG
INVECCHIAMENTO E SINDROME DI WERNER
REGOLAZIONE ENDOCRINA DELL’INVECCHIAMENTO
STUDIARE VERMI E INSETTI
PER CAPIRE L’UOMO
Drosophila melanogaster
Coenorabditis elegans
adulto
L4 embrioni
L1
L2
L3
Circa 3 giorni a 22°C
CICLO VITALE DI C.ELEGANS
adulto
L4 embrioni
L1
MANCANZA DI ALIMENTI
CICLO VITALE DI C.ELEGANS
STADIO DAUER
LARVA LARVA DAUER
Studio di processi biologici legatia una maggiore morbidità
l’esempio dell’invecchiamento
DAF1 (IGF-R)
AGE 1 (IP3-K)
DAF 16* DAF 12
DAUER
DAF 7 ( TGFb ligand)
DAF 4 (Type II TGFbR)
DAF 3, DAF 5 (SMAD prot)
DAF9 (cytochrome CCYP27A1)* Proteine della famiglia FOXO coinvolte nel metab del glucosio
SIR2 (deacetilasi attiva di DAF 16)
3-keto-cholestenoic acid metabolite
Insulin/IGF-1 Insulin/IGF-1 IGF-1 Insulin
GH
DAF 2 receptor
DAF 16/FOXO (adip. Tissue)
LONGEVITY
TOR
germline
dFOXOTOR
germline
LONGEVITY
IGF-1R 1R
LONGEVITY
Invecchiamento e ambiente
SEXUAL REPRODUCTION
“REGULATORS”
NUTRIMENT AGE
“EFFECTOR”
EVOLUTION: LAND OF BIOLOGICAL EQUAL OPPORTUNITIES
SEXUAL REPRODUCTION
NUTRIENTS
AGE
• FECUNDITY SHOULD BE DIRECTLY PROPORTIONAL
TO NUTRIENT AVAILABILITY,
• HIGH NUTRIENT AVAILABILITY, FAVORING FECUNDITY, SHOULD
SHORTEN THE LIFE SPAN
DEATH: A TOOL INDISPENSABLE TO ENSURE THE CONTINUATION
OF THE SPECIE
but
EVOLUTION: LAND OF BIOLOGICAL
EQUAL OPPORTUNITIES
Intrinsic program for aging aiming at increasing the fraility of the organism:
a biological clock(telomers length, mitochondrial viability; DNA replication errors, loss of immune
control and inflammation…)
sex-dependent (male fecundity cannot be limited as well as in females)
Fertility-driven
Extrinsic factors
nutrition adaptable environment
AGING
AS NECESSITY FOR THE CONTINUATION OF LIFE and
AS A MEAN TO GIVE TO EACH INDIVIDUAL EQUAL POSSIBILITIES TO GIVE HIS GENETIC CONTRIBUTION TO THE
NEXT GENERATION