KOVARI LECTURE OBJECTIVES/NOTES Flashcards Preview

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Flashcards in KOVARI LECTURE OBJECTIVES/NOTES Deck (92)
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1

What biochemical events are triggered by growth factor binding to specific receptors?

GF binds to CELL SURFACE receptors (transmembrane proteins with a CYTOPLASMIC PROTEIN KINASE DOMAIN) causes: 1. immediate increase in intracellular Ca2+ (indicates initiation of transmembrane signaling) 2. Reorganization of actin stress fibers: necessary for anchorage dependence of cell attachment that is required for cell cycle progression 3. Activation, nuclear translocation, or both, of transcription factors: TF bind to regulatory regions of DNA of genese that are responsive to GF to induce cell cycle machinary 4. DNA synth + Cell division **GF activates distinct combination of signal transducers and TF to dictate precise gene induction and causes characteristic responses (classes)

2

How do growth factors regulate the cell cycle?

Growth factor signals generated at the plasma membrane can transduce gene induction, cell cycle progression, and proliferation, differentiation, or apoptosis; GF triggers TF activation that regulate induction of components of the cell cycle machinery that monitor and direct cell cycle progression, cell growth arrest, and cell differentiation. Induction of DNA damage that would result in the accumulation of mutations leads to cell cycle arrest and DNA repair; alternatively, if the DNA damage is too great, cell death occurs by apoptosis

3

Summary of aging:

aging = result of chronic chemical modification of all classes of biomolecules According to Free radical theory of aging, ROS = causes changes in DNA sequence (mutations) and therefore changes the protein structure; Longevity = achieved by developing efficient systems to limit and or repair chemical damage; CR = delays aging and extends mean and max lifespan of specific by inhibiting the production of ROS and decreasing damage to biomolecules and delaying many characteristics of aging, including cancer

4

Describe the microscopic structure of the liver

= lots of lobules; each with a polyhedral shape blood sinusoids = from terminal branches of the portal vein; interconnect and interweave through the sheets of hepatocytes before joining the central lobular vein Sinusoids are lined by two types of cells: 1. vascular endothelial cells (loosely connected one w/another); leave numerous gaps, forming a net-like lining to the sinusoids; no basement membrane b.n the endothelial cells and hepatocytes thus allowing for exchange of metabolites b/n plasma and hepatocyte 2. Kupffer cells = mononuclear phagocytes = generally found in the gaps b/n adjacent endothelial cells (immune functino in protecting liver agains infection)

4

Describe the relationship between aging and disease

aging = time dependent deterioration in function of an organism that changes the cell structure and function; result = increased susceptibility to disease AGING IS NOT A DISEASE! Diseases affect a fraction of a population, and aging affects everyone Aging is associated with decreased functionality in biochemical and physiological systems (decreased BMR, protein turnover, glucose tolerance, telomere shortening, decreased lung, cardiovascular, musculoskeletal, nerve conduction, etc.) Humans survive till age 50 without maintenance, with 76 = mean lifespan. lifespan is affected by our genetics and our environmental exposure and death is usually attributable to failure of a critical system death rate = max at mean lifespan; max lifespan = 120 year.

5

Describe the regulation of the cell cycle

Growth factors stimulation induces proteins that are involved in regulating the cell cycle including: cyclins and CDKs (cyclin-dependent kinases) Cyclins = proteins that are specifically degraded at every mitosis CDK = kinase that must bind to a cyclin in order to be active The activity of cyclins is modulated by changes in expression at transcription and translation level; activity of CDK = modulated by phosphorylation state (expressed in relatively constant amts) SO: GF --> + cyclin --> + CDK + CDKI CDK-I = CDK inhibitor (binds to CDK and blocks catalytic activity) cyclins = have a specific CDK they are associated with and together they act at different stages of the cell cycle

5

Differentiate between biological and chemical theories of aging

Biological = aging is a genetically controlled event that is determined by the programmed expression or repression of genetic information. sees aging as birth, growth, maturation, reproduction, death stages; differences in lifespan among a species are closely correlated with the efficiency of DNA repair mechanisms (more efficient DNA repair = longer lifespan); Chemical = aging is a somatic process that results from cumulative damage to biomolecules; 1. error catastrophe theory proposes that aging is the result of cumulative errors in the machinery for replication, repair, transcription, and translation of genetic information; errors lead to accumulation of dysfunctional macromolecules that cause an increasing amount of immunological detectable, but denatured or modified, functionally inactive, enzymes accumulating in cells as a function of age 2.other chemical theories of aging = result of chronic, cumulative chemical (non-enzymatic ) modification damages all biomolecules; damage is most apparent in long-lived tissue proteins (lens crystallin and extracellular collagen); brown color commonly results from formation of a wide range of conjugated compounds (also crosslinking occurs!) sort of like malliard reactions in which bread crusts; chemical integrity to the genome also occurs AGE DEPENDENT MODIFICATIONS: 1. protein modifications (ie: crosslinking, oxidation, deamination etc.) 2. DNA modifications and mutation (ie: depurination, oxidation, point mutations) 3. inactive enzymes 4 lipofuscin

6

What is the role of apoptosis in cellular development?

= programmed cell death necessary to maintain integrity and homeostasis of multicellular organisms; inapropriate apoptosis can lead to degenerative conditions (neurodegenerative disorders) and disruption can lead to cancer or autoimmune disease; 2 key families of enzymes regulate apoptosis: 1. caspases (cysteine protease) 2. BcL-2 (Bcell lymphoma protein2): regulates caspase activity

7

what are some of the characteristics of infectious agents found only in prions?

dont require DNA/RNA like others! -extremely resistant to inactivation (by UV light, xrays and chemical agets) -no humoral immune or inflammatory response -no virus like particles -can be inherited

8

Summary of cancer:

in cancer: proto-oncogenes and tumor suppressor genes = function in signal transduction to mimic the effects of persistent mitogenic stimulation in order to continue the passage of the cell through G1 and present cell cycle exit. 2 suppressor proteins = p53 and Rb = key roles in determining cell cycle progression and apoptosis and the genes for coding the proteins are most frequently disrupted in cancer cells.

8

What is the relationship between hierarchy of protein structure and protein folding diseases?

primary structure (aa sequence) predisposes protein towards its native conformation; folding = spontaneous, but mechanisms depend on: nature of perimary solved (H20 vs lipid) concentration of salts, pH, temperature, and molecular chaperones Native conformation (tertiary structure) = determines biological function (catalysis, protection, regulation, signal transduction, storage, structural , transport) in conformation disorders, the biological function is affected a loss or change of structure may lead to loss of function

9

Rb gene vs Retinoblastoma

Rb gene = tumor suppressor gene (regulates cell cycle) Rb disease = rare; deletion of a specific band on chromosome 13; a single somatic mutation to knock out the remaining copy of Rb gene was sufficient to initiate a cancer Rb disease = rare, but mutations in Rb are not and occur in more common cancers such as lung, breast, and bladder carcinomas

9

What is the role of chaperones in folding and misfolding?

= proteins that prevent faulty folding and unproductive interactions between other proteins; -some are induced by conditions that cause unfolding of newly synthesized proteins -bind predominantly to hyrdophobic regions of unfolded /aggregated proteins they act as a quality control/editing mechanism for detecting misfolded/defective proteins most are associated with ATPase activity they can be found in cytosol, mitochondria, or lumen of ER (like prions.. proteins that are unconventional infections again )

10

Describe the life cyle of a retrovirus (like HIV)

Adsorption of virus to a specific receptor (ie: CD4+ on T-cell to CD4+ receptor on HIV) causes viral penetration which allows reverse transcriptase activity to start (ssRNA to dsDNA); the dsDNA is incorporated into the host genome for translation of host and viral genome to proteins and capsid to allow for budding of a new viral molecules; therefore to stop HIV proliferation, need to block both viral and host proteins for replication

11

what are the mechanisms of proteolysis? (protein catabolism in the liver)

increased plasma ammonia or decreased urea = biomarkers of impairment of protein catabolism

12

Describe the etiology and pathology characteristic of several disease of accelerated aging

Progerias = diseases of accelerated aging caused by defects in DNA repair (biological aging) Werners Blooms syndrome = autosomal recessive; due to mutation of DNA helicase genes that have a role in replication and repair of damaged DNA Werners = premautre aging starting in teenage and the development of diseases early on, leading to death by 40 due to heart disease Alzheimers disease = appearance of neurfibrillary tangles and senile plaques in the cortical brain (AGE/ALE increased in tangles/plaques); oxidative stress = strongly implicated in development or progression of AD and chelators are being evaluated clinically for treatment of AD

13

what is a prion? Describe Creutfeldt-Jakob disease)

prion = protein in misfolded form that causes infection and induce healthy, properly folded proteins to be converted into a disease associated with misfolded prion forms Prp = protease resistant protein Scrapie PrP = infectious form of PrP Normal PrP + Sc PrP = amyloid (insoluble protein) Bovine Spongiform encephalopathy (BSE) = mad cow disease (from cattle that were fed diseased sheep/cattle); BSE transmitted from cattle to humans (CJD) incubation time varies from 4-40 years old ***CJD = due to prion, so it CAN be inherited, but it is STILL INFECTIOUS

14

Describe how HIV binds/fuses/replicates in a host cell

HIV: has two strands of ssRNA and reverse transcriptase inside the virus; GP41 on lipid membrane and GP 120 (receptor for CD4+ ) on top of gp41 (for co-receptor) T-CELL: has CD4+ receptor on cell surface, and co-receptor (CCR5 and CXCR4) how: HIV and gp120 bind to CD4+ on T cell, and the co-receptor then binds to HIV (gp41) and allows fusion an penetration of viral RNA into the T-cell host; then RNA to unintegrated linear DNA via reverse transcriptase and then the DNA gets integrated into the host DNA for proteins and virus budding

15

What are the major mechanisms in cell signaling?

Polypeptide (ie: insulin) binds to extracellular receptor, induces a signal cascade resulting in induction of transcription factors that act on DNA to increase gene expression; Cell-Cell interaction and/or Nitric Oxide (intracellular) also trigger the signal cascade Steroid hormones (pass through membrane) and act on an INTRACELLULAR receptor (transcription factor) that causes an increase in gene expression response = phagocytosis, apoptosis, proliferation, exocytosis, secretion

15

What is the role of mutations in cancer

a single mutation is not sufficient to convert a health cell to a cancer cell; several rare mutation need to occur together (usually~3-7 independent mutations are necessary) Mutations in DNA occur spontaneously at a rate of 10^-6 mutation per gene per cell division; so every human genes is likely to undergo mutation on about 10^10 occasions; incidence of mutations increases exponentially with age spontaneous and induced mutations cause tumors: naturally occuring = point mutations, deletions, translocations Carcinogenic compounds, UV, Xrays, and viruses = increase the rate of mutations

15

Describe the biochemical and genomic structure of HIV (a retrovirus)

3 main sites on genome: 1. GAG (has p24; proteins) 2. POL (contains protease and reverse transcriptase; all enzymes) 3. ENV (envelope; contains GP120 that binds to CD4+ and other proteins) Human retrovirus has 2 copies of single stranded RNA with GP120 and GP 41 on surface on the lipid membrane; and reverse transcriptase is inside ** there are many variations of HIV-1 which makes it complex and difficult for drug development

15

Describe the relationship between viral load and the disease progression

initially the immune system can control the disease and during clinical latency the viral load remains pretty stable (but CD4+ decreases) then by the onset of AIDS, viral load increases a lot and the CD4+ decreases a lot; the lower the viral load = less severe the disease

16

How do tyrosine kinases participate in signal transduction?

After dimerization of the receptor, the intracellular domain becomes transphosphorylated and the tyrosine kinase activity is stimulated; tyrosine phosphorylation of receptor creates 'docking sites' that allow protein-protein interactions, leading to recruitment and activation of SIGNALING ENZYMES or ADAPTER MOLECULE; PTK = enzymes that transfer gamma-phosphate group of ATP to tyrosine residues on target substrate proteins = rapid and reversible covalent modification that changes enzymatic activity of target proteins; Signal transducers recruited to Tyr-Pi via protein-protein interaction domains (SH2 domains) contained within the signal transducer; SH2 = Src homology region 2 = specifically recognize a phosphotyrosine and the 3 aa immpediately C-terminal to the phosphotyrosine

17

What is the role of receptor dimerization?

Growth factor binding usually induces receptor dimerization and activation of the tyrosine kinase intrinsic to receptor; ligand binding to the extracellular domain triggers dimerization; this causes a conformational change in the cytoplasmic domain and transphosphorylation that activates the tyrosine kinase catalytic activity

18

What is AIDS?

Acquired Immunodeficiency Syndrome that causes gradual destruction of cell mediated (T-cell) immunity therefor increases susceptibility for infection/cancer); caused by HIV; transmitted by blood contact or bodily fluid (infected mother to fetus transfusions can occur)

18

What are the three pathophysiological effects of HIV infection?

1. Immunodeficiency = opportunistic bacterial and viral infections and unusual cancer 2. Autoimmunity = production of autoimmune antibodies, arthritis, 3. Neurologic dysfunction = AIDS demtia complex, HIV encephalopathy, neuropathies

19

Describe the relationship of the liver and protein metabolism; plasma proteins? what are the changes in hepatic protein synthesis that take place during the acute phase reaction?

decrease in albumin or an increase in prothrombin time indicate impairment of protein synthesis! majority of plasma proteins are synth in the liver; albumin = most abundant protein in the blood (made only in the liver!) ceruplasmin = copper containing ferroxidase ferritin = stores iron transferin = transports iron alpha-fetoprotein = if high, associated with liver cancer measure hepatocyte synthesis function via measuring the production of coagulation factors II, VII, IX, X because all undergo post-translational gamma carboxylation of glutamyl residues (so they can bind Ca2+) in the liver; acute phase protein response = all systemic changes that occur in response to infection or inflammation magnitude of APP response shows the progress in a disease and its response to treatment; ie: [CRP] (C-reactive protein) is used as a marker for infection/inflammation (concentration may increase by a magnitude of 1 or 2 orders!)

19

Describe Heme catabolism

Heme --> bilirubin via heme oxygenase to biliverdin (IM) to bilidrubin via biliverdin reductase *bascially: Heme rind uses O2 and reduction equivalent to open up the ring = bilirubin; excess bilirubin = jaundice Normally: RBC --> spleen for destruction (spleen stores scenescent RBC and unconjugated bilirubin) --> unconjugated bilirubin is complexed with albumin in the blood--> bilirubin is taken up into liver for conjugation with glucouronic acid --> MAJOR PATHWAY: conjugated bilirubin --> urobilin --> feces (coloring = due to bilirubin) MINOR PATHWAY: conjugated bilirubin to urobilin to urine (through KIDNEY)

19

what is the role of cytochrome p450 in the metabolism of drugs?

3 genes of cytochrome P450 = for drug metabolism: CYP1 CYP2 and CYP3; each gene has multiple allels; the P450 enzyme encoded by CYP3A4 gene appears to be involved in te metabolism of most drugs; How it works: 1. drug joins P450 Fe3+ 2. NADPH gets oxidized to NADP+ and P450-Fe3+-drug gets reduced to P450-Fe2+-drug; occurs via NADPH cytochrome P450 Reductase 3. Oxygen joins (now P450-Fe2+-drug-O2) 4. Reduction of Fe2+ to Fe3+ via H+ joining O2 to make H2O that leaves 5. No have P450-Fe3+-drug-OH 6. drug-OH leaves P40-Fe3+; now it can bind to another drug molecule and drug-OH can be excreted. OVERALL REACTION (MEDIATED BY P450) RH + O2 +2H + 2e- --> ROH + H2O (where R = drug)

20

Describe the trends in HIV as an epidemic

started as a gay man's disease, but now increased infection due to heterosexual contact and injection drug use; there is a decrease in overall prevalence it is more prevalent in men than women generally, except in africa (slightly more women/equal) globally = 40 million individual; africa = 26.2 million estimated incidence of AIDs and AIDS related deaths are decreasing; LARGE decrease in perinatally acquired AIDS because of treatments decreasing its transmission; also even in an untreated woman only 25% of children will inherit disease due to placenta blood barrier