Final Exam Flashcards
Nematode Aging
LET-363 and Target of rapamycin promote aging
Daf-2 and insulin/IGF-1 receptor to daf-16/FOXO stop aging
Fruit Fly Aging
Target of rapamycin promotes aging
dINR and insulin/IGF-1 receptor to dFOXO stop aging
Mouse Aging
Target of rapamycin promotes aging
Growth of hormone to IGF-1, IGF-1 receptor and insulin receptor to FOXO1 and FOXO3 stop aging
RNA interference (RNAi)
Post-transcription gene silencing; double-stranded RNA (when introduced into a cell) causes sequencing-specific degradation of homologous mRNA sequences
Argonaute
One of the main components in RISC; cleaves and discards the passenger strand of the siRNA duplex leading to activation of the RISC
Dicer
RNAase 3 enzyme
siRNA
21-23 nt short interfering RNA
RISC
RNA-inducing silencing complex
ER stress
Physiological and pathological stimuli disrupt the ER homeostasis, resulting in midfielder and unfolded proteins
Unfolded Protein Response (UPR)
ER stress activated complex signaling network to reduce ER stress and restore the ER homeostasis
Three aims of UPR
1) restore normal function of cell by stopping protein translation
2) degrading midfielder proteins
3) activating signaling pathways that increase the production of molecular chaperones in protein folding
If not achieved, UPR aims towards apoptosis
BIP
Immunoglobin biding protein
ATF6
Activating Transcription Factor 6
Not required for longevity phenotype of daf-2 mutants
XBP1
X-box binding protein 1
New ER stress response, longevity genes leads to improved ER homeostasis
PERK
PKR-like ER kinase
IRE1
Inositol Requiring 1
Required for longevity phenotype of daf-2 mutants
ERAD
ER-associated protein degradation
Pek-1
Not required for longevity phenotype of daf-2 mutants
Sir-2 and daf-16
Sir2 stimulates daf-16 activity to increase worm survival
14-3-3 and sir2 are required for daf-16 to function
RAS Signal Pathway components
SOS, GAP, ERK, RAF, MEK, FOS
SOS
Guanine nucleotide exchange factor (first in pathway)
GAP
GTPase activating protein (after SOS)
ERK
Extracellular signal-regulated kinases
RAF, MEK, ERK
Protein kinase phosphorilation cascade (follows GAP)
FOS
Transcription factor
Cell proliferation, differentiation, and survival (end of pathway)
Inhibition of RAS
Extends fly lifespan
RAS dominate negative mutants
MEK inhibitor and what it does
Trametinib
Extends fly lifespan
Trametinib
MEK inhibitor; approved for use with dabrafenib for untraceable/metastatic melanoma with BRAF mutation
14-3-3 protein name
Name refers to elution and migration pattern of proteins on DEAE-cellulose chromatography and starch-gel electrophoresis
14-3-3 ability
Ability to bind a multitude of functionally diverse Signaling proteins
Includes kinases, phosphatases, and transmembrane receptors
What 14-3-3 does
14-3-3 binding variably regulates its partners, ranging from positive to negative regulation via several different mechanisms
Bonds specific phosphoserine/threonine motifs on the target protein
14-3-3 First major mode of action
binding can alter ability to target protein to interact with other proteins (bind with IRS-1 attenuated ability to recruit and activate PI-3 kinase)
14-3-3 second major mode of action
Binding can modify the target protein localization which causes its target’s exclusion from the nucleus and it’s retention in the cytoplasm
14-3-3 third major mode of action
Can bridge two proteins together, serving as a phosphorylation dependent scaffold protein
14-3-3 forth major mode of action
Binding can alter the intrinsic catalytic activity of the target protein, inhibit or augment it’s function
14-3-3 fifth major mode of action
Binding can protect the target protein from other modifications such as dephosphorylation and proteolysis
Sirtuin (or Sir2 proteins)
Sir2 - silent information regulation 2
Required for lifespan extension resulted from glucose restriction in yeast cells
Are protein deacetylases dependent on nicotine adenine dinucleotide (NAD) and are found in organisms ranging from Baxter to humans
Various enzyme activities (mono-ribosyltransferase and deacylase)
Overexpression of Sir2
Extends lifespan of C. elegans, Drosophila, and mouse
In C. elegans, promotes nuclear localization of DAF-16/FOXO transcription factor
Saccharomyces cerevisiae, three different kinds of loci subject to gene silencing
Silent mating-type loci, telomeric regions, rDNA repeats
Accumulation of rDNA circles; Extrachromosomal rDNA circle (ERC)
A young cell — excision/inheritance of ERC — replication, recombination, asymmetrical segregation (can repeat this step) — old cell, nucleolar fragmentation, death
Deacylase activity
Important for lifespan regulation
Depends on NAD level, which links it’s enzymatic activity directly to energy status of cell via cellular NAD:NADH ratio
Nicotinamide adenine dinuleotide (NAD)
Extends C. elegans lifespan
What does Sirtuins (NAD+ dependent deacetylases) do
Remove acetyl groups from lysine residues within proteins in the presence of NAD+
Yeast Sir2
A histone deacetylase
Sir2 enzyme activity results
Results in tighter packaging of chromatin and a reduction in transcription at the targeted gene locus: telomeric sequences, the hidden MAT loci (HM loci) and the ribosomal DNA locus
Seven sirtuins in mammals
Sirt1 - homologous of Sir2, overexpression mimics diet restriction
Sirt2 - mainly expressed in brain
Sirt3, Sirt4, Sirt5 - active in mitochondria
Sirt6 and Sirt7 - active in nucleus of cell
Overexpression of sirt6
Decreases level of phosphorylated AKT
Decreases level of phosphorylated FOXO and S6K
INCREASES LONGEVITY OF MALE MICE - reduces IGF signaling pathway in white adipose tissue
Resveratrol
Red wine
Sirt1 activator SRT1720
Extends lifespan and improves health of mice fed standard diet
What does Resveratrol do
Improves health and survival of mice in a high-caloric diet
Autophagy definition
A catabolic process involving degradation of a cell’s own components through the lysosomal machinery
Autophagy: first type
Chaperone-mediated: a cytosolic chaperone protein recognizes and binds proteins to form a substrate-chaperone complex delivered to the lysosome through lysosome-associated membrane protein (LAMP) type 2A
Autophagy: second type
Microautophagy: a direct engulfment if cellular components by invagination of the lysosomal member
Autophagy: third type
Macroautophagy: process in which cytosol and organelles are sequestered within double-membrane vesicles that deliver the contents to the lysosome/vacuole for degradation and recycling of the resulting macromolecules
Biological functions of autophagy
Survival during starvation anti-aging differentiation and development protection against neurodegeneration innate immunity cell growth control/tumor suppression cell death
When does autophagy occur
Misfolded protein goes to phagosomes/lysosomes, which goes to autophagy
Telomere definition
A region of repetitive nucleotide sequences at the end of a chromosome, which protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes
About telomere
Shorten with each cell division
Estimated that human telomere lose about 100 base pairs from their telomeric DNA at each mitosis
Cellular senescence
Triggered when telomere are on average 4-6 kb
Telomere Hypothesis of Aging
Telomeres shorten with age (tissue with high cell turnover); therefore, telomere shortening is a cause of aging
Telomerase definition
An enzyme that adds telomere repeat sequences to the 3’ end of DNA strands
Reverse transcriptase that carries its own RNA molecule, used as a template when it elongates telomeres
Long telomeric DNA
Long lifespan in worms
p53
Guardian of the genome
Cell cycle arrest — DNA repair — cell cycle restart — cellular and genetic stability
Apoptosis — death and elimination of damaged cells — cellular and genetic stability
Progeria / Hutchinson-Gilford Progeria Syndrome (HGPS)
Extremely rare genetic condition wherein symptoms resembling aspects of aging are manifested at an early age
1 per 8 million live births
Diseased live to mid teens and early twenties; occurs as a new mutation and is rarely inherited
Werner syndrome
An autosomal recessive disorder. WRN gene associated with this syndrome lies on chromosome 8 and it’s the only gene known to be associated with Werner syndrome.
Caused by mutation in the WRN gene which codes a DNA helicase that functions 3’ to 5’
What is observed in Werner syndrome
Increase telomere attrition and genomic instability
Rapid telomere decay is thought to play a causal role in the clinical and pathological manifestations of the disease
