Week 1 Flashcards
Endosymbiont Hypothesis and evidence
Mitochondria arose early in evolution of eukaryotic cells by endocytosis of bacteria capable of oxidative phosphorylation
Mitochondria has unique structure similarities to bacteria
- Inner membrane derived from bacteria
- Outer membrane derived from eukaryotic cell
Mitochondria Import across the outer membrane is ________ and occurs when _________ interacts with ____________
passive, facilitated diffusion
N-terminus of protein (containing highly positive sequence) interacts with very negatively charged domain in GIP channel
Mitochondria import across the inner membrane is _____ through ______.
Process?
ATP dependent
through TIM23/22 gated channel
- N-terminus (+) sequence bids channel, opens it
- Protein unwound by ATPase chaperone and fed through channel unfolded
- Channel closes immediately after protein comes through in order to maintain proton gradient
Oxidation of NADH –> NAD results in ________, creating a ___________ and ________
release of one e- that goes through electron transfer through 4 protein complexes embedded in inner mitochondrial membrane
- proton concentration (1 e- –> 5 H+ pumped across)
- Electrical potential (- matrix, + outside)
ATP is produced from the ________ and _________
proton gradient and electrical potential
ATP synthase spans _______ and is made up of 2 complexes ______ and ______.
ATP synthase flips through 3 conformations key for function:
inner membrane
F1 protein complex
Fo protein complex
1 - bind ADP and P
2 - forms an ATP
3- loses affinity for ATP
F1 protein complex (ATP synthase)
actual enzyme that makes ATP
-Bound to Fo
Fo protein complex (ATP synthase)
uses energy of proton movement through the channel to generate ATP
-3 H+ needed for 1 ATP
ATP is transported out of mitochondria via __________
ATP-ADP antiporter
Mitochondria role in regulating cell death due to cell damage
Cell damage → Bak/Bak-dependent permeabilization of outer-mitochondrial membrane → cytochrome C release
Cytochroms C → formation of apoptosome protein complex
Mitochondria role in regulating cell death due to ischemic injury
Ischemic injury → MPTP-dependent permeabilization of inner and outer mitochondrial membranes
→ cytochrome release
No ATP present due to lack of O2
Results in necrosis (instead of apoptosis)
Mitochondrial fusion occurs to __________. _____ and ______ proteins do this
repair damaged mitochondria
OPA1 and Mfn 1/2 GTPases
Mitochondrial fission occurs for _________ and is carried out by ______ and ______ proteins
for mitophagy
GRP1/BAX or Fis1/Drp (depending on if you look at ppt or handout…)
Mitochonrial Quality control occurs via these three processes
- Fusion and fission (occurs regularly, vital for maintaining mitochonria)
- Proteolytic degradation
- Mitophagy
If these all fail, mitochondria will trigger apoptosis
Proteolytic degradation in mitochondria….
done by which two proteases?
Detects defect in enzyme → extract and replace with a new one
Done by sIII, and mAAA proteases that recognize and degrade protein
Mitophagy
• Mitochondria badly damaged enough, gets eaten up
AD optic atrophy and Charcot-Marie-Tooth neuropathy
caused by mutations in OPA and Mfn2 (respectively) mitochondiral fusion proteins
Mutation in mAAA protease results in _________
hereditary spastic paraplegia
Release of ROS by mitochondria results in _______ and _________
senescence and increased sensitivity to neuronal degeneration
Arsenic poison works by…
inhibiting oxidative phosphorylation and ATP production
Features of epithelia (5)
- Adherent to one another
- Cells arranged in one to several layers
- Polarized (asymmetric)
- Undergo turn-over/renewal (Driven by epithelial stem cells)
- Avascular (nutrients must diffuse through CT and basal lamina)
Apical surface =
Basal surface =
Apical surface = outer surface, directly exposed to fluids or environment
Basal surface = inner surface, connected to underlying connective tissue via basal lamina
Epithelial cell functions (7
o 1) Barrier – protects internal tissues
o 2) Selective absorption and transport of molecules from the environment
o 3) Selective secretion of molecules and fluids
o 4) Movement of particles and mucous through passage ways
o 5) Biochemical modification of molecules
o 6) Communication to and from other tissues and organs
o 7) Reception of sensory stimuli (e.g. smell, taste, touch)
Endothelium = ? Mesothelium = ?
Endothelium: tissue that faces blood and lymph
-Made of endothelial cells
Mesothelium: sheets of cells that line the enclosed internal spaces of the body cavities
- Made of tightly adherent cells
- Free surface faces blood/lymph, and rests on basal lamina
Epithelial classifications:
simple
stratified
Pseudostratified
Simple: cells arranged in a single layer
Stratified: more than one layer, outer layers do not directly contact basal lamina
-Named according to outermost layer
Psuedostratified: some cells reach the free surface, but all directly rest on the apical to basal axis
Epithelial classifications:
Squamous
Cuboidal
Columnar
Transitional
- Squamous: flattened cells
- Cuboidal: cube-like
- Columnar: taller than they are wide
- Transitional: e.g. bladder - stratified, but when stretched, change shape from cuboidal to squamous and appear to decrease in layering
Spatial Relationship between layers of epithelia
space (lumen) → Epithelia-epithelia basal lamina → CT → CT embedded tissues (blood vessels, muscle, nerves – all with their own basal laminae that connects them with the CT)
Epithelial to Mesenchymal Transition
o Occurs during embryogenesis
o Embryonic epithelia often disassemble and move into the mesenchymal (connective) tissues and migrate to other locations to form new epithelia
• Mesenchyme = developmental precursors for many other tissues
o Cells can also transform into distinct non-epithelial cell lineages that give rise to other tissues
Cellular basis for apical-basal polarity of epithelial cells
1) Plasma membrane composition locally segregated into domains
- Membrane in apical domain contains distinct membrane proteins and phospholipid content compared to the basal domain
2) Cytoplasm is polarized
- Cytoskeleton is asymmetric – organelles distributed in precise, polarized pattern
- Secretory vesicles in apical different from basal
Functions of polarity (4)
1) Allows unidirectional secretion/absorption of molecules to or from one side of the epithelium
2) Trans-epithelial transport
3) Transcytosis
4) Important for localizing intercellular signaling among epithelial cells, or between epithelial cells and other cell types
Trans-epithelial transport
transport of ions and molecules from apical to basal or vice versa
Transcytosis
endocytosis of substances from one membrane region, trans-cellular transport of vesicles, and exocytosis from another membrane region
Tight Junction
2 key proteins?
-Highly selective barrier, limits/prevents diffusion of substances between epithelial cells
Key proteins: occludins and claudins
“Tightness” of this barrier can be regulated
-Tight → ensures substances absorbed/secreted must pass through the epithelial cell by specific transport pathways
Adherence Junctions
Key protein?
Promote attachment, polarity, morphological organization, and stem cell behavior within epithelial sheet
Key proteins: cadherins
Cadherins are ______ with _______ and ________ domains that act to…
Transmembrane proteins
Extracellular domains - interact with each other
Cytoplasmic tails – bind adapters/signaling proteins and ACTIN filaments
Cadherin associated proteins
(e.g. B-catenin, protein kinases)
control aspects of epithelial polarity, development and function
Desmosomes
Key proteins?
Promote mechanical strength, resist shearing forces, promote structural organization of epithelial sheet
Key proteins: different class of cadherins
Link to INTERMEDIATE FILAMENTS and other adapter proteins
Gap junctions
Promote rapid communication between epithelial cells, through diffusion and small molecules
Microvili
- actin-containing protrusions, connected to cytoskeleton in cell interior
- Increase surface area → increases transport and secretion across membrane
Stereocilia
type of microvili
- Found in sensory cells in ear
- Very long, actin-filled microvilli
- NOT related to cilia
Cilia
3 types
microtubule-containing protrusions
Primary, Motile, and Sensory Cilia
Primary Cilia
single non-motile extension
-Promote signal transduction systems that control epithelial cell division, fate, and function
Motile Cilia
motile, found on specific epithelia cells
- Move mucous and other materials along passageways
- In respiratory tract, oviduct
Sensory Cilia
non-motile, function in sensory reception
-Connect sensory systems with CNS
Basal Lamina
-Thin sheet of EXTRACELLULAR material
- Underlies basal surface of each epithelial tissue (including muscles, nerves, and blood vessels)
- Separates epithelial cells from connective tissue
- Attaches epithelial cells to extracellular matrix on CTs
- Formed by collagen networks
- Synthesized and secreted by epithelial cells
Specific attachments of basal lamina?
connect basal surface to basal lamina
Integrins
Focal Adhesions
Integrins
strengthens epithelial-CT attachment
- connect intermediate filaments to epithelial cell
- Protein-protein interactions
Focal adhesions
connect actin filaments inside cell to basal lamina
-Regulate cell polarity, function in signaling
Exocrine glands
- secrete materials onto epithelial lined surfaces or the outside world
- glands are CT, but remain connected to epithelia apical surface from which they formed
- Secrete contents onto surface of epithelia – ALWAYS on APICAL surface
- contain ducts and secretory units
Secretory units
clumps of secretory epithelial cells
-Organized into bowl-shaped lobules called alveoli (acini) or into tubes (tubular glands)
Ducts
tubular structures, emanate from secretory units
-Passageways for secretion
Endocrine glands
- secretes substances into the blood stream (no ducts)
- Endocrine glands detach from parental epithelia
- Organized into clumps or cords of cells embedded in CT (isolated from lumen from which they formed), surrounded by basal lamina, with extensive capillary network
- ALWAYS secrete hormones into blood from BASOLATERAL membrane that act over long distances
Endocrine hormone pathway:
cross basal surface of gland cell and basal lamina then basal lamina and endothelial layer of capillary to reach blood stream
Epithelial stem cell properties (5)
1) Capable of dividing – re-enter cell cycle to produce new cells
2) Self renewal – when they divide, always reproduce themselves (the mother cell) to maintain stem cell populations in the body
3) Produce differentiated progeny
4) Tightly regulated
5) Structural organization – tied to distinct type of tissue
2 key principles of epithelial stem cell signaling pathways
1) Each pathway used by multiple, distinct stem cell systems in different organs/tissues
2) A single signaling pathway often triggers different developmental outcomes in different stem cell lineages
- Due to different developmental histories, different environments, and different levels of signals/receptors
Stem cell regulation
- Stem cell division and differentiation VERY tightly regulated → stem cells divide slowly and infrequently
- Stem cells thus much less abundant than differentiated offspring
Transit Amplifying cells – divide rapidly and differentiate
Loss of regulation → disease
Carinoma
cancer of epithelial origin
-Result from defects in regulatory pathways that control epithelial stem cells and their progeny during tissue development and maintenance
Adenocarcinoma
cancer derived from glandular epithelium
Cystic Fibrosis gene
AR inheritance (carriers asymptomatic)
CF gene: large ATP-binding transporter gene
- Chr7
- Encodes for Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) protein
CF protein
CFTR
- Expressed in epithelial cells (lungs, pancreas, etc.)
- ATP-binding
- Functions as an epithelial ion channel that controls the movement of salt and water into and out of cells
Classes of CF mutations: class 1 class 2 class 3 class 4 class 5
Class 1: non-sense or frame-shift mutation → no synthesis of CFTR protein
Class 2: block in processing and maturation in ER
Class 3: block in regulation (gating mutation)
-Protein on cell surface, but it is closed
Class 4: altered conductance
-CFTR at cell surface, but not working
Class 5: reduced synthesis, lower amounts of receptor on the membrane
Pathophysiology of CF lung disease
Normal: Peri-cilliary fluid layer lines tubes and cilia of out epithelial cells
Without CFTR → no Cl- moves out of cell → hyper-absorption of Na+ into cell, and water follows → thick dehydrated, sticky mucous layer lining epithelial cells
Ivacaftor
CFTR modulator protein rescue drug
- Targets class 3 gating mutation
- Binds → conformational change in CFTR protein that allows improved chloride transport
- Reduces chloride sweat values
Lumacaftor
CFTR modulator protein rescue drug
- targets class 2 mutation (del/del genotype)
- Corrector plus potentiator
- Helps 50% of CF population
Components of cilia (4)
1) Basal body anchor
2) Axoneme
3) Transition Zone
4) ciliary membrane
Basal Body
- Core anchors from which cilia are formed
- Organizes ciliary axiome
- Microtubule rich
- Central hub with 9 fold radial symmetry
- 3 microtubules per subunit
Axoneme
- Structural skeleton of cilium, provides tracks for movement within cilia
- made of doublet MTs
Intraflagellar Transport (IFT) uses _______ to go in the + direction and ________ to go in the - direction
- kinesin + IFT-B protein complex → +
* dynein + IFT-A protein complex → -
Transition Zone
- Links basal body to axoneme and ciliary membrane
- “Gatekeeper”
- Limits diffusion of membrane and soluble proteins into/out of cilium
- Ensures ciliary membrane is a distinct compartment for cellular signaling
-Defects highly associated with ciliopathies
Ciliary membrane
Continuous with plasma membrane but compositionally distinct
Cilia Assembly (2 Steps)
1) centroles/basal bodies assembled
2) Formation of cilium
Centrole/Basal Body formation
Basal bodies derived from centrioles
Mother centriole functions as basal body/anchor
Centriole duplication during G1 to S phase with DNA duplication
-Once-and-only-once, tightly regulated
Formation of cilium
- Ciliary vesicle caps basal body → microtubule doublets assemble into ciliary vesicle → fuses with plasma membrane of the cell
- Cells with many cilia per cell use many basal bodies (uncoupled from cell cycle and replication)
Structural distinctions between motile and sensory cilia
MOTILE:
- 9+2 microtubule arrangements
- 9 doublet MTs around central pair of singlet MTs
- Some motile cilia have 9+0 arrangement
- KEY: Contain axonemal dynein arms between the doublet microtubules
SENSORY:
- 9+0 MT arrangement
- No axonemal dynein arms
Why are cilia good for signaling?
- High receptor surface-volume ratio
- Signal localized and polarized with discrete cell domains
- Receptors positioned away from interfering cellular domains
- Cilium can function as a mechanical detector of flow
- Sense physical stimuli, light, and chemical stimuli
Hedgehog (Hh) signaling
importance of cilia in development
→ limb formation, bone formation, neurogenesis
Ciliary Nodes
importance of cilia in development
-establish left-right body asymmetry
- Invagination of ciliated cells (9+0 organization)
- Beat in a rotary fashion to produce leftward flow of signaling molecules
- Signals detected by non-motile sensory cila at periphery of ciliary node → organogenesis
Bardet-Biedl Syndrome (BBS)
Ciliopathy
-BBS proteins participate in protein complex required for vesicle transport within cilium
Polycystic Kidney Disease (PKD)
-AD and AR forms (AD more common)
- AD = mutation in polycycstin 1/2
- AR = mutation in fibrocystin
- Mutation in channel proteins responsible for Ca2+ signaling
- Sense mechanical flow of urine in kidney lumen
Symptoms:
- Renal cysts
- Liver and pancreas cysts
- Intracranial aneurysms
Adult stem cells are _________, NOT ______________.
PLURIPOTENT not todipotent
Pluripotent → give rise only to the cells of that tissue
Mesehchymal Cells
precursors to all connective tissue family members
-Primarily function in embryogenesis, but some persist through adulthood as stem cells for generation of new connective tissues
Fibroblasts
- Secretory machines – produce fibrous proteins, proteoglycans, and ECM components
- Capable of cell division to make new fibroblasts or differentiate into other CT cell family types (myofibroblasts, adipocytes, chondrocytes, osteprogenitors)
- Highly regulated
- Proliferation stimulated by tissue injury
Myofibroblasts
- derivatives of fibroblasts
- Do contractile function for CT
- Generated at wound sites for scar tissue
Adipocytes
- derivatives of fibroblast
- Stores fat as energy for other cells
White fat vs. brown fat
in Adipocytes
In adults it is “white fat”, in newborns and children it is called “brown fat” (high in mitochondria, convert fatty acid into heat)
Lymphocytes are involved in…
acquired immunity to foreign organisms, viruses, and materials
Macrophages
large “engulfing” cells
-Differentiate from monocytes
Function of macrophages (5)
1) Phagocytosis of cells, ECM, and invaders
2) Promote/control angiogenesis
3) Send other signals to other cells
4) Remove damaged tissue, remodeling of repaired tissue
5) Remodel normal developing tissue/organs during morphogenesis
Neutrophils and Eosinophils are involved in defense against…
defense against microorganisms
Mast cells
- secretory cells activated by immune response
- Differentiate from basophils
- Promote vasodilation and swelling in CT
- Important in edema and allergic hypersensitivities
Types of connective tissue family cells (5)
1) Mesenchymal cells
2) Fibroblasts
3) Myofibroblasts
4) Adipocytes
5) Osteoblasts/ Osteocytes/ Osteoprogenitors
Types of connective tissue immigrant cells (5)
Lymphocytes Macrophages Neutrophils/Eosinophils Mast Cells Osteoclasts
ECM is made up of ______ and _______ as well as many other ___________ embedded within or diffusing through the ECM
structural fibers and ground substance
extracellular macromolecules
Collagen is the _________ fiber of the ECM.
most abundant structural fiber
One collagen molecule = ?
3 intertwined a-chain polypeptides –> form multimeric cross-linked collagens