M2M Unit 4 Flashcards
origin of mitochondria
current theory: endosymbiotic hypothesis
showed up by way of endocytosis of oxidative-phosphorylating bac by distant ancestors
inner membrane is derived from bac
outer membrane is derived from eukaryotic cell
outer structure of mitochondria
double membrane (only other double membrane organelle= nucleus)
outer membrane- semi-permeable, regular membrane
-have TOMS (translocases of outer membrane: large, nongated channels allowing H+’s, etc to equilibrate w/ the cytosol, permit passive transport)
inner structure of mitochondria
inner membrane- less permeable, forms the folds/cristae inside the mito, contains machinery for ox-phos
-have TIMS (translocases of inner membranes- specific receptor-based protein channels allowing various required proteins selectively in, require ATP input
- cristae has 4 protein complexes to pass e-‘s from NADPH to various e- acceptors (ending in O2 to form H2O), generating E w/ each transfer
- small steps to minimize E lost and harness at each step
-matrix space inside inner membrane
contains mito’s own DNA (although majority of proteins that func in mito come from cell nucleus)
e-‘s transferred and protons (NADPH–> NADP+) are pumped out of matrix, at which point they can leak out of outer membrane
- creates a chem gradient w/ more negative charge inside the matrix
- drug target- disrupting the gradient quickly kills cells
in high E consumption environments- use creatine kinases to keep PO4 on creatine; can quickly transfer it to ADP to make ATP
fission/fusion of mitochondria
undergo constant fusion/fission
both dependent on GTPases
fusion- role in repairing damaged mito and maintaining integrity
- no SNARE proteins
- has to fuse both membranes
- GTPase Mfn and OPA1
fission- mitophagy
-GTPase Fis1 and Drp
mitochondria-regulated death mech
apoptosis
cell damage induces Bak/Bax-dependent permeabilization of outer-mito membrane
leads to cytochrome c release
cytochrome c binds to proteins and forms apoptosome
apoptosome- activates caspases (initiating apoptosis)
mito-regulated death mech
necrosis
during ischemic injury
results in MPTP- dependent permeabilization of inner/outer mitochondria membranes
results in cytochrome release and elimination of H+ gradient
-no H+ gradient blocks ATP production
-ATP synthase converted to ATPase, using up available ATP
-ATP depletion and necrosis
mitochondria quality control
damaged mito:
can’t produce ATP
generates excessive ROS
ROS oxidizes proteins, lipids, DNA –> cell damage and senescence
controlled on 3 levels:
- mito proteases (mAAA, iAAA, Lon) recognize and degrade misfolded proteins
- damaged mito can be “fixed” by fusing with healthy mito or can be eliminated by mitophagy
- induced apoptotic death if damage is extensive
role of mito in senescence
inc sensitivity to neuronal degeneration and senescence related to accum of mito damage and ROS
-neuropathies w/ mito quality control pathway protein mutations
optic atrophy (OPA1 gene- auto dom)
Charcot-Marie-Tooth neuropathy Type 2A (Mfn2 gene)
–both from mito fusion machinery mutation
hereditary spastic paraplegia- mutation in mAAA protease
-ox-phos and ATP prod inhibition from Arsenic poisoning
epithelial define
tissues that line all surfaces of the body, internal (gut, glands, tubes, ducts, etc) and external (skin)
make up business ends of many organs
most cancers derived from epithelia
functions of epithelia
barrier to microorganisms and toxins
selective transport into and out of body
biochem modification of molecs and metabolites (detox in liver)
specialized reception of stimuli (taste receptors)
self-renewal
epithelial properties
highly adherent to e/o to form sheets, often wrapped to form tubes
most are polar (apical and basal surface- allows for unidirectional transport)
basal lamina layer found underlying all epithelia
all epithelia are attached on basal side to CT beneath basal lamina
-CT has vasculature (epithelia does not)
-blood needs to diffuse through CT to reach epithelia
-important for self renewal
-(CT also has nerves and muscle w/in it)
-note cells lining vascular sys are called endothelia
epithelial cells during development
become mesenchymal cells
migrate through body to form new regions of epithelia (epithelial-to-mesenchymal transition)
-some tumors act this way- reactivate the mesenchymal transition, migrate through the body and metastisize
types of epithelial cells
simple vs stratified
- pseudostratified
- transitional stack type- normally stratified but don’t stretch it
cuboidal, columnar, squamous
stratified are classified based on outermost layer
epithlial polarity
molec/protein composition is different on 2 sides
tight junc’s between epithelial cells prevent membrane components from getting to the other side
cytoskeletons are polarized- which makes organelles inside epithelia polarized too
epithelia tight junctions
hold adj cells together
made of transmembrane proteins (most are occludens)
wrap all around the cell
prevent flow of molecs from apical to basal side
basis of impermeability of epithelia- forces substances in the lumen (water, ions, etc) to go through cells vs between them
some epithelia are looser than others- found in intestines (quick, massive tranport of water/ions in paracellular transport)
tight junctions can be loosened/tightened dep on what is being transported (loose for glucose, ex)
-substances on basal side can leak out into lumen if junctions are loosened
epithelia adherens junctions
specific regions that are punctiliar
AKA desmosomes
no barrier functions- just to bind adj cells together
caused by variety of specialized proteins called cadherins
cadherins- bind with e/o in presence of Ca.
can regulate tightness of specific cell junctions
epithelia gap junctions
small tunnel/channel between intracellular regions of 2 adj cells
selectively allows the flow of small molecs (like signaling) between cells (to speed up broad response to stimuli)
3 cell surface modifications of epithelia
microvillae
cilia
stereocilia
microvillae
pouches on the apical side of epithelia cells
increases surface area of apical surface
filled w/ actin, generally
cilia
hairlike structures
move substances by rhythmic motion
made of microtubules powered by dynein motors
sterocilia
found in cochlea of ear
seem to be important in stimulus reception
basal lamina structure
thin sheet made of interlocking proteins
some proteins are common to most laminae (like type IV collagen) but others are unique to particular tissues
functions of basal lamina
- promote attachment of epithelia to underlying CT
- regulate epithelial cell bio (through focal adhesion signaling)
- barrier func- barrier to movement from epithelial layer to CT; generally not very strong
- specialized types can act to filter specific molecs (specifically glomerulus)
2 kinds of basal lamina attachment
hemidesmosomes
-contain integrins that provide membrane attachments to the epithelial cells and other protein complexes that link CT to lamina
focal adhesions
- specialized hemidesmosomes
- connect basal lamina to intracellular components inside the epithelial cells
- allows signaling communication between lamina and epithelium
- allows lamina to influence the dev/regulation of epithelium
exocrine glands
secrete agent molecs onto epithelial surfaces
- dev as simple invaginations of the epithelium
- synthesize variety of sub’s
- have to cross the apical membrane to get to the “outside” of the epithelial cell
-secretory units- invaginated pouches that function as exocrine glands
these make secretions and transport them across the apical membrane and flow down the narrow part of invagination to reach the outside of the epithelium
-don’t always have invaginations; sometimes just single cells prod/secreting
types of exocrine secretions
mucus secretions
serous secretions- watery; sweat, saliva, etc.
endocrine glands
always secrete agents into blood
dev as invaginations of the epithelium that are pinched off from the epithelial surface
surrounded by vessels in CT
synthesize hormones
generally cross basal membrane and get through CT and vessel surfaces to get to blood
exception: thyroid endocrine hormones
- secrete through apical membrane, mature in lumen, and transported across both membranes out again
epithelia regulation
most have self-renewing potential via specialized stem cells, stored in “crypts” or pouches at the bottom of epithelial sheets
-tightly regulated; few of them, spread out, slowly dividing
polarity of cell proliferation- new cells push up old cells and old migrate toward apical
further differentiated as they migrate
regulatory proteins of epithelial stem cells: Wnt proteins
Wnt proteins in the colon inhibit differentiation by dividing at the cell surface and setting off a signaling cascade; also promote cell division (more differentiation= less division)
normally APC protein inhibits Wnt signaling pathway in colon
(blocking APC activates cell proliferation)
APC mutation–> colon cancer
similar proteins in lung, but opposite pathways
Wnt promotes differentiation and inhibits division
epithelial cancer
generally called carcinoma
adenocarcinoma- cancers derived from glandular epithelia
high levels of cadherin activity correlate w/ higher survival rates
could be from:
tighter connections between epithelial cells lead to less metastasis of epithelial cancer cells, or
cadherins can act as signaling molecs to sense cancer and respond appropriately
visualizing tissue samples
tissue sample is cut out, put in saline buffer, and fixed (soln to preserve large cell structure)
-carbs and lipids tend to leak out in process
sample sliced thinly and stained to create 2-D image (general to specific)
tip: find nuclei
immunohisotochemistry
immunofluorescence
methods of detecting presence of particular proteins in pathology slices- info about quantity and loc of protein
use antibodies- have high affinity and specificity for certain proteins/antigens
method: fix and stain
apply primary antibody (sticks to pertinent protein); wash
add secondary antibody (sticks to primary antibody) w/ a colored tag; wash
look at color
protein defect in Cystic Fibrosis CF
most common lethal genetic disease in caucasians
CF gene codes for CFTR protein- acts as apical ion channel controlling water and ions moving out
large CF gene on Chr 7; multiple pathological mutations
mutations cause:
no protein synthesis
misfolding, leading to degradation before reaching apical cell surface
altered conductance so protein can’t be conveyed to apical surface
partial loss-of-func so CFTR proteins don’t work normally
pathophysiology behind CF lung disease
pseudomonas and staphyloccus aureus are the most common pathogens found in CF lungs
CFTR normally excretes Cl- to move water into mucus layer overalying the lung epithelium
defective CFTR- water doesn’t move
-also high levels of Na+ import, which further removes water from lumen/mucus
chronic lung problems- chronic bronchitis and airway infection/inflammation
-lead to loss of lung func
diagnostic and therapeutic approaches for CF
major diagnostic- test for Cl level in sweat
-large levels of Cl- indicate homozygosity for CF (auto recessive)
positive NBS
treat- lungs w/ airway clearance therapy antibiotics to keep lungs clear inhaled mucolytics (breakup mucus) bronchodilators ERT VitA, D, E, K replacement Azrithromycin used chronically
therapeutic-
eventually need lung transplant
“protein rescue” seems promising to fix misfolding/nonconduction problems
cilia components
domains: centriole/basal body axoneme transition zone ciliary membrane intraflagellar transport (IFT) machinery
cilia basal bodies
core anchors from which cilia are formed
microtubule rich cylinder shaped structures form from 9 triplet microtubules
polarized structure
responsible for nucleating cilium
cilia axoneme
structural skeleton of cilium
provide tracks for movement within cilila
formed from doublet microtubules assembled from basal body
polar
lengths range from
cilia transition zone
links basal body to axoneme
considered “gatekeeper” because it limits diffusion in/out of cilium
ensures compartmentalization for signaling
mutant transition zones associated with ciliopathies
ciliary membrane
continuous w/ cellular plasma membranes
compartmentalized by transition zone, so it’s a distinct membrane with unique phospholipids and receptor molecs
cilia IFT
transports cargo for assembly/maintenance of cilium and for movement of signaling components within cilium along the axoneme
bidirectional transport w/ kinesin motors and the IFT-B protein complex directing movement to ciliary tip (anterograde transport)
retrograde transport- cytoplasmic dynein 2 motor driven transport with the IFT-A protein complex
both transport mech’s are required for cilium formation and func
cilia assembly
2 phases- centrioles/basal bodies assembly and formation of cilium
centrioles interchange func at centrosomes and making basal bodies; upon cilogenesis, the older of the 2 centrioles in G1/S phase funcs as basal body/anchor
ciliogenesis- normally in G1 (or G0)
distal end of basal body is capped by ciliary vesicle; microbutuble doublets assemble into ciliary vesicles before structure fuses w/ plasma membrane
terminally differentiated cells nucleate many cilia per cell; require more mech’s (basal body assembly uncoupled from cell cycle; replication is amplified)
motile vs sensory cilia
motile- most also possess sensory func’s
required for fluid movement in resp, neural, and repro tracts
motility produced by axonemal dynein dependent sliding motion between the doublet microtubules of cilliary axoneme
typically 9+2 microtubule arr; 9 doublets around central pair of singlet microtubules (not all have central)
sensory- immotile/primary cilia
9+0 microtubule arr
lack axonemal dynein arms
normally perform signaling funcs
cilia signaling pathways
cilium concentrates the singal w/ a high receptor surface-to-vol ratio signal is localized and polarized within discrete domains receptors are positioned away from interfering cellular domains func as a mechanical detector of flow
can sense physical stimuli, light, chem stimuli; all produce range of downstream events:
proliferation, motility, polarity, growth, differentiation, tissue maintenance
cilia hedgehog signaling pathway and others
Hh signaling pathway
well established to signal through cilia
activation and repression of the target of the Hh paracrine signaling pathway (glioma tumor- Gli transcriptional activator) requires cilia
Wnt, PDGF, FGF, and others
cilia in tissue homeostasis
Hh signaling:
limb formation, bone formation/homeostasis, neurogenesis
tissue and cellular polarity organogenesis tissue patterning (neuronal and limb) bone formation cell fate specification eye dev left-right-axis determination craniofacial dev neural tube formation tubule formation (kidney, liver, pancreas) renal cystic diseases and retinal degeneration (degenerative)
clinical abnormalities associated with ciliopathies
cystic kidneys nephronophthisis obesity polydactyly retinal degneration aminosa (loss in olfaction) cancer/tumorigenesis urinary tract malformation cognitive impairment diabetes mellitus infertility occipital meningoencephalocele microphthalmia lung hypoplasia renal hypodysplasia or displasia bile-duct dilatation situs inversus
Bardet-Biedl Syndrome BBS
autosomal recessive ciliopathy
19 genes mutated in BBS patients to date
BBS proteins participate in a protein complex that is required for vesicle transport within the cilium
symptoms: photoreceptor degeneration anosmia mental retardation/developmental delay neural tube defects obesity hypogonadism kidney defects polydactyly diabetes
mesenchymal CT cells
precursors to all CT family members
primarily func in embryogenesis, but small numbers of them may persist through adulthood to fun as stem cells for generation of new CTs
fibroblasts
the pre-eminent cells of most CT in body
not really a single cell type
look similar histologically but express different markers and proteins in dff tissues
