Lecture 16 - 22 Flashcards
1
Q
What is diabetes mellitus?
A
The inability to regulate blood glucose
2
Q
What is the normal levels of glucose and what is the diabetic level of glucose?
A
Normal = 5mM
Diabetes = 7mM+
3
Q
What is the pathogenesis for type I diabetes?
A
- caused by a failure of insulin secretion
- character sized by low insulin and high glucose levels
- has sudden onsets
- caused by the destruction of beta cells
4
Q
What is the pathogenesis of type II diabetes?
A
- caused by insulin resistance in tissues
- insulin present in circulation but glucose remains elevated
- has gradual onset
5
Q
How does insulin-dependent diabetes mellitus (type I occur)?
A
Beta cells of pancreas are destroyed by cytotoxic CD8 T cells reactive against peptides of insulin and other specific proteins which are complexed with MHC molecules and recognized by cytotoxic T lymphocytes
6
Q
What are the symptoms of hyperglycemia?
A
- increased fluid osmolarity in tubules
- more water is secreted from cells into the proximal convoluted tubule
- causes increased urine floe (dieresis)
- water reabsorption is reduced
- dehydration, excessive urine production and thirst
7
Q
What is hyperglycemia?
A
When high glucose concentrations enter glomerular filtrate and overwhelms the glucose absorbing capacity of the proximal convoluted tubule
8
Q
What are the forms of insulin used for therapy?
A
- animal insulin (porcine/bovine)
- human insulin
- human insulin analogue
9
Q
What are the types of human insulin and what are their characteristics?
A
- Soluble insulin
- rapid and short lived
- used intravenously in emergency treatment of hyperglycemic. - Isophane insulin
- tends to form precipitates = intermediate acting - Insulin zinc suspension
- tends to form precipitates = long acting
10
Q
What are the three insulin analogues and what are their characteristics?
A
- Insulin Lispro
- modified insulin obtained by switching a Lys28 and Pro29
- very rapid and very short lived.. usually taken before a meal - Insulin glaring
- modified insulin obtained by mutating Asn21 in Gly and by adding 2 Arg at the end of the beta chain - Insulin detemir
- modified insulin obtained by mutating Thr 30 (deletion)
11
Q
How does type 2 diabetes occur?
A
Beta cells try to compensate for peripheral resistance = beta cells become exhausted and cannot keep up with the peripheral demand of insulin = failure of insulin secretion
12
Q
Which cell is responsible for the autoimmune reaction that destroys the beta cells of pancreas in type 1 diabetes?
A
CD8 cytotoxic T cells
13
Q
Which of the following is NOT a feature of type 1 diabetes?
A. Sudden on-set
B. Develops early in life
C. Rare
D. Caused by failure of insulin secretion
E. Caused by peripheral insulin resistance
A
E. Caused by peripheral insulin resistance
14
Q
Which of the following combinations of insulin forms would be normally used to control glycaemia?
A. Lispro + soluble insulin
B. Zinc suspension + Glargine
C. Soluble insulin + glargine
D. Lispro + detemir
A
C & D: Soluble insulin + glargine, Lispro + detemir
Has to be a short acting + intermediate long acting
15
Q
What are the order of events in type 2 diabetes?
A
- Obesity/ sedentary life style
- Hyperinsulinemia
- Beta cells failure
- Hyperglycemia
- Retinopathy
16
Q
What molecules can lead to insulin resistance in type 2 diabetes?
A
IL-1 & DAG
17
Q
Which of the following drugs work by improving insulin secretion from the beta cells of the pancreas?
A. Pioglitazone
B. Beta-3 receptor agonists
C. Gliclazide
D. Metaformin
E. Insulin
A
C. Gliclazide
18
Q
What is the role of free fatty acids in insulin resistance?
A
- lead to insulin resistance in muscle and liver
- when in excess they are transformed into secondary messenger DAG
- DAG activates PKC which phosphorylate IRS-1 = attenuates insulin receptor signal
19
Q
What is the role of Adipokines in insulin resistance?
A
- released by Adipocytes
- adiponectin is anti-hyperglycemic = improves insulin sensitivity by activating AMPK = promoting lipolysis in liver and muscle
20
Q
What is the role of inflammation in insulin resistance?
A
- adipocytes produce IL-6 and IL-1 which attract macrophages to fat deposits
- experimental reduction of cytokines improve insulin sensitivity
21
Q
What is the role of PPARgamma in insulin resistance?
A
- promotes secretion of anti-hyperglycemic adipokines
- mutations can cause diabetes
22
Q
What is the role of Thiazolidinediones (Pioglitazone)?
A
- Agonist of nuclear receptor PPAR-gamma
- promotes expression ad secretion of anti-hyperglycemic adipokines = increases lipolysis
- reduce insulin resistance in liver and their peripheral tissues
23
Q
What is the role of Metformin?
A
- suppress glucose release from liver
- activate AMPK
- increase lipolysis in liver and muscles = improve insulin receptor signaling
- suppress glucose release from liver
24
Q
What is the role of Sulphonylureas (Gliclazide)?
A
- bind to sulhponylurea receptors expressed on membranes of beta cells
- block ATP sensitive K+ channels in Beta cells
- K+ accumulates inside cells = beta cells depolarize
- Ca2+ channels open = allow insulin secretion by exocitosis
25
What are the 2 types of drugs for type 2 diabetes?
1. Alpha2 adrenoreceptor antagonist
- increase insulin secretion
2. Selective beta3 agonists
- beta3 adrenoreceptors control lipolysis in fat cells
26
What are the long term consequences of diabetes?
- ROS = high levels of glucose in our blood cause oxidation in long term excess of glucose = reactive oxygen species
- AGEs generation = binds to receptor and induces the production of reactive oxygen species that damage blood vessels
27
How is NF-kappaB activated in the canonical/classical pathway?
- formed by a dimer of p50 and RelA
- pathway activated by the binding of a ligand to the receptor which activates a complex of IkB kinases
- kinases complex will phosphorylate IkB causing IkB ubiquitination and then IkB is degraded
- p50 and RelA are free to enter the nucleus and cause the transcription of specific target genes
28
How is NF-kappaB activated in the non-canonical pathway/alternative signalling pathway?
- activation of kinases NIK phosphorylate IKKAlpha which phosphorylate p100
- processing of p100 via proteosome to form p52 = associates with RelB to cause transcription of the genes in the nucleus
29
What is the role of Rel Homology Domain (RHD)?
encodes the DNA binding and dimerisation functions of NF-kappaB
30
What is the role of p100 and p105?
contain ankyrin repeats in their C-termini that allow them to function as IkB inhibitors
31
What are TA1/TA2, TAD, SD1, SDII?
non-conserved transcriptional activation domains
32
What are the subunits in the canonical pathway?
- p50
- RelA
- c-Rel
33
What are the subunits in the alternative pathway?
- RelB
- p52
34
What are the inhibitors of NF-kappaB?
IKBA, IKBB, IKBE and Bcl-3
35
What do the IKB proteins contain?
contain ankyrin repeat motifs (ANK) in their C termini. PEST, domain rich in proline (P), glutamate (E), serine (S) and threonine (T).
36
What does Bcl-3 contain?
nuclear coactivator for the p52 NF-κB subunit (and other transcription factors)
37
How does NF-kappaB cause cancer?
control of NF-kappaB is lost = NF-kappaB in cytoplasm causes the transcription of genes = uncontrolled proliferation of cells
38
What is the structure of p53?
- N-terminal domain contains a sub-transactivation domain and a proline-rich domain which is involved in regulation of apoptosis.
- Core domain bind to specific DNA sequences
- C-terminal domain contains the tetramerization domain
39
What is the p53 signalling pathway?
1. p53 binds to an inhibitor HDM2
2. stimuli activates p53 and is recognised as an oncosurpressor
3. when activated p53 the inhibitors are degraded so p53 is free
4. p53 can repair DNA or induce apoptosis if the DNA cannot be repaired
40
What is the difference between NF-kappaB and p53?
NF-kappaB = tumor-promoting functions
p53 = tumour suppressing functions
41
What needs to happen to carry out a cell cycle?
- chromosomes need to be duplicated
- other organelles need to be copied
- cells need to grow
- chromosomes need to be segregated accurately
- cell needs to physically divide
42
What drives the cell cycle?
cyclin-dependent kinases (Cdks)
43
What are Cdks?
protein kinase that transfer a phosphate onto their substrates = act as master regulators
44
What makes cyclin levels oscillate?
Mechanisms controlling synthesis = changes in transcription and translation rate
45
What is the role of the APC/C signal?
signals degradation of M-cyclin to end mitosis and initiate cell division
46
What is the role of the SCF signal?
signals degradation of CKIs to promote G1-S transition
47
How is cell cycle fidelity maintained?
- cyclin oscillations provide timing for the successive phases of the cell cycle = checkpoints monitoring the cell cycle to make sure everything is in place
48
How do checkpoints in the cell cycle work?
act by promoting Cdk activation or inactivation
49
What are mitogens and their role in the cell cycle?
proteins that signal the cell to proliferate = promotes G1/S synthesis
50
What is the role of DNA damage in the cell cycle?
inhibits M phase cyclin activity by phosphoregulation or CKI
51
What is the role of unattached chromosomes in the cell cycle?
prevents M phase cyclin destruction = cell stays in M phase until chromosomes are attached
52
What does the G1 checkpoint check?
- if nutritional conditions are stable
- if the cell is receiving proliferation signals
- if damaged DNA has been repaired
53
What does the G2 checkpoint check?
- if damaged DNA has been repaired
- if DNA replication is complete
- if the cell is big enough
54
What does the mitotic/spindle assembly checkpoint check?
- of the chromosomes are properly attached to the spindle
55
What happens if a checkpoint cannot be satisfied?
Cells will resume the cell cycle if errors or damage can be fixed.
if not
Cells can withdraw from the cell cycle (senescence)
-Terminal exit from cell cycle
-Allows cell to remain part of tissue but it will not proliferate
Or:
Cells can undergo programmed cell death (apoptosis)
- Removes cell from organism
56
How can cells trigger the transcriptions of G1-S cyclins?
Early G1 genes (Myc) can react to mitogens and bind to cell-surface = activates and increases the transcription of several genes
57
What genes are activated and increased in G1/S transition?
- cyclin D
- SCF ubiquitin ligase (for protein proteolysis)
58
What are temperature sensitive mutants?
Mutants that allow gene products to function at low temperature but not higher temperature
59
Why do we use temperature sensitive mutants?
To track cell cycle by size and budding
60
What triggers the degradation of M-cyclin?
APC/C
61
What is the role of the poly ubiquitin chain on cyclins?
Chains of ubiquitin form a tag that the cell recognizes as a destroy signal = cyclin moves to proteosme to be destroyed
62
What are the 4 groups of Cdks?
1. G1-Cdks = Cdk 4 & 6
2. G1/S Cdks = Cdk2
3. S- Cdks = Cdk2 & Cdk1 (CDC2)
4. M-Cdk = Cdk 1 ( CDC2)
63
What are the 3 groups of cyclins?
1. G1 cyclins = Cyclin D
2. G1/S cyclins = Cyclin D, cyclin E, cyclin A
3. G2/M cyclins = cyclin B
64
What type of division occurs in mitosis?
Equational division = each of the daughter cells have the same numbers of chromosomes that we started with (in parental cell)
65
What type of division occurs in meiosis?
Two division steps
1. Reductional division = start with 2 sets of chromosomes San end up with one set
2. Equational division = start with one set of chromosomes and end with one set of chromosomes
66
What needs to happen in PROPHASE (mitosis)?
- chromosomes begin to condense
- centerosomes (which organize microtubules) move apart = form a bipolar spindle
- nuclear membrane breaksdown
67
What needs to happen in PRO-METAPHASE (mitosis)?
- chromosomes attach to spindles/microtubules
68
What needs to happen in METAPHASE (mitosis)?
- chromosomes align in the middle of the cell (metaphase plate)
- microtubules teach onto chromosome centromeres
69
What needs to happen in ANAPHASE (mitosis)?
- chromosomes are separated onto opposite poles via spindle fibers
70
What needs to happen in TELOPHASE (mitosis)?
- chromosomes decondense
- nuclear envelope reforms
- process of cell division begins
71
What needs to happen in CYTOKINESIS (mitosis)?
- cell pinches into 2 separate cells
71
What needs to happen in CYTOKINESIS (mitosis)?
- cell pinches into 2 separate cells
72
What is the role of M-Cdk?
Regulates cell entry into mitosis
73
How does M-Cdk work?
Directly phosphorylate key substrate proteins to change the cell into a mitosis state.
- regulates downstream mitotic kinase (aurora B and Cyclin B kinases) which phosphorylate additional substrates
74
What is the kinetochore?
The microtubules binding site on a chromosome
75
How does assembly of microtubules occur in prophase?
- Phosphorylation of M-cyclin and Aurora B recruit new proteins to assemble microtubules in early mitosis
76
What is the structure of the kinetochore?
- large macromolecular complex that assembles on the centromere
77
What proteins/kinases are needed in the kinetochore?
- M-Cdk (Cyclin B-Cdk1) & Aurora B required to recruit kinetochore proteins in early mitosis
78
What is the role of cohesion rings?
Cohesion rings entrap two pieces of DNA = brings 2 pieces of DNA together and force cohesion
79
What happens when chromosomes condense in prophase?
- Cohesin is removed
- condensing are recruited
- interphase chromosome structure is lost
- mitotic structure is gained
80
What is the structure of microtubules?
Alpha and beta tubule dimmers that have a minus an d plus end
81
What does gamma-TuRC do?
Nucleates proteins at the minus end of microtubules to trigger the assembly of tulip into polymers
82
What are the different types of microtubules and what do they do?
1. INTRAPOLAR MICROTUBULES = interact with each other across the spindle
2. ASTRAL MICROTUBULES = project away from the centrosome and contact the cell cortex
3. KINETOCHORE = microtubules that bind to chromosome
83
What are the roles of Microtubules adapter proteins (MAPs)?
Allow cell components to bind microtubules = modulate the stability of microtubules (whether they grow or shrink)
84
What is the role of Ndc80/Nuf2?
Modulates the stability of microtubules at kinetochores
85
What is the roll of motors?
Allow cell components to move along microtubules (moves chromosomes around)
86
What is the role of Kinesin-5?
Walks to the plus end of the microtubules
87
What is the role of Dynein?
Walks to the minus end of the microtubules
88
How do Kinesin motors function?
Use ATP energy to “walk” along chromosomes
89
How does Kinesin-5 carry cargo?
Forms dimmers and cross-links microtubules ( cargo is another kinesin-5 molecule)
90
How does CENP-E carry cargo?
Binds to kinetochores (cargo is a kinetochore)
91
How does mitotic spindle assembly occur?
- nucleation of microtubules at centrosomes (minus end)
- formation of interpolar microtubules and sliding moves centrosomes apart
- nuclear envelope breakdown allows microtubules to capture kinetochores
92
What is the role of conversion of lateral attachment?
conversion of lateral attachment to end on attachment is a critical part in getting to a bi-orientated state.
93
How does conversion of later to end-on attachments occur?
Once a kinetochore reaches the + end of a microtubule, the means of attachment changes.
End-on attachments require the Ndc80 complex (Ndc80 and Nuf2)
94
What is the role of the kinase Aurora B?
Detects bi-orientation by localizing to centromeres and phosphorylates Ndc80 to remove microtubules from kinetochores
95
What does the spindle checkpoint check for?
Detects any unattached kinetochores
96
What do unattached kinetochores produce?
Produce the mitotic checkpoint complex (MCC)
97
What is the role of the MCC?
MCC inhibits the APC/C by acting as a stop signal = prevents M-cyclin degradation which keeps cells in mitosis
98
What happens when all kinetochores are occupied with microtubules?
MCC is no longer produced and M-cyclin is degraded, cell exits mitosis
99
What is securin?
Inhibitor of protease named separase = cleaves cohesin in the centromere and removes the attachments between the two sister chromatids
100
What happens in anaphase A?
Chromosomes moves towards the spindle poles
- driven largely by microtubules depolymerization at the plus end of kinetochore microtubules
101
What happens in Anaphase B?
Spindle poles move apart.
- Driven largely by microtubules motors e.g kinesin-5
102
What happens in telophase?
- nuclear envelope reforms and nuclear pores are inserted
- chromosomes decondense
- condensins dissociate
- cohesin re-associate and enable the formation of chromosome looping structures needed for correct gene expression
103
What is the importance of asymmetric cell division in development?
Critical for multicellular organisms to differentiate from a single cell into many tissue types
104
What is the role of ACD in normal stem cells?
ACD balances proliferation and self-renewal with cell-cycle exit and differentiation
105
What is the difference between the two types of asymmetric cell division?
INTRINSIC:
- relies on internal factors within the cell to divide
- when cell divides, factors will be inherited by one daughter cell only
EXTRINSIC:
- don’t rely on intrinsic factors within the cell to divide
- promotes the self-renewal/proliferation capacity of stem cells
- mitotic spindle is orientated prior to division
106
How does asymmetric cell division of germ cells support their immortality?
- forms 2 cells = one with “junk” of the cell and one that becomes a sex cell
- germ cells allow for the preserve cells of the genome that is passed from parents into offspring.
107
How is cell polarity established?
Established through PARs
108
What does the polar axis show?
Polar axis within the cell indicates that one side of the cell is different from the other
109
What are the 2 ways that centrosomes signal polarity?
1. Regulating the myosin cytoskeleton
2. Pathway that depends on the microtubules that are emanating from the centrosome
110
What happens in regulating the myosin cytoskeleton?
- as centrosomes mature, they emanate Aurora A kinase factor = impacts the organization of the myosin cytoskeleton
- advection
- foci assemble and disassemble
111
What is the structure of myosin cytoskeleton?
Network of actin filaments interfering with myosin motors
112
What is advection?
PAR proteins are being moved without contact
113
What happens in the pathway that depends on the microtubules that are emanating from the centrosomes?
- microtubules prevent kinase from the anterior pass to act upon posterior parts and remove them from the membrane.
- domains are maintained by mutual antagonism
114
In fruit fly asymmetric division what happens when the embryo delaminates?
Polarity is inherited by the epithelium it was residing in
115
What happens when PARs are removed?
Both spindle poles migrate to the exterior
116
What doe LGN promote?
Promotes the formation of complex on the apical membrane = important for the rotation of the mitotic spindle
117
What are the steps for centrosome stereotypical positioning?
1. Centrosome is recruited to the apical crescent
2. Daughter centrosome remains apical and presents more microtubules polymerization activity = mother centrosome shreds PCM
3. Favoring the orientation of the forming spindle
4. Mother centrosome will be inherited by the cell undergoing differentiation
118
What is PAR1 and what is its function?
PAR1 = a posterior PAR protein = phosphorylates MEX-5 which leads to segregation of MEX-5 to the anterior
119
What are P-granules?
A condensate of proteins and RNAs that mix from the cytoplasm without the need for a membrane
120
What is the difference between P-granules and MEX-5?
P-granules become enriched in the posterior
MEX-5 become enriched in the anterior
121
What do APC targets promote?
Promote differentiation and inhibit cell renewal
122
In what ways do aPKCs inhibit cell renewal?
1. NUMB = inhibitor of Notch signaling
2. MIRANDA = directs the localization of..
- Staufen = mRNA binding protein
- Prospero = transcription factor
- Brat = protein translation inhibitor
123
How does cell fate specification occur?
Through aPKC phosphorylation
- when aPKC encounters Miranda it phosphorylates it and removes it from the membrane
124
How does the division of the two cells occur in cytokenisis?
Through the action of the contractile ring = formed by actin filaments and myosin motors.
Upon pulling the myosin motors = constriction of ring = division of the two cells
125
What are the 4 groups of CDKs?
1. G1-CDK: CDK4 & 6
2. G1/S-CDK: CDK2
3. S-CDK: CDK2 & CDK1 (CDC2)
4. M-CDK: `cdk1 (CDC2)
126
What are the 4 groups of cyclins?
1. G1-cyclin: cyclin D
2. G1/S cyclin: cyclin E
3. S-cyclin: cyclin A
4. G2/M cyclin: cyclin B
127
What are the 3 main checkpoints that coordinate cell cycle progression?
1. restriction point (START in yeast)
2. G2/M (DNA damage) checkpoint
3. Mitotic checkpoint
128
How does chromosome duplication occur in the cell cycle?
Chromosome is replicated in S phase and are held together in G2 (cohesion).
129
How does centrosome duplication occur in the cell cycle?
Happens in S phase along with DNA replication.
130
How does the golgi, ER and mitochondria duplication occur in the cell cycle?
disassemble and then vesiculate as cells go into mitosis.
131
What is the role of SCF?
signals degredation of CKIs to promote G1-S transition
132
What is SCF?
it is a ubiquitin ligase
133
What is the role of APC/C?
signals degradation of M-cyclin
134
What is the role of ubiquitinylation?
it is a tag for protein degredation
135
How do checkpoints act?
act by promoting Cdk activation or inactivation
