Baumann und Seyfried Flashcards
response strength depends on
concentration of the signal
curve can be: all-or-nothing
sigmoidal
hyperbolic
Surface receptor act via signaling cascade. At teh target protein that can lead to
altered…
gene expression
shape and movement
metabolisim
small (monomeric) G proteins mediate…
gene expression
cytoskeleton
membrane traffic
nuclear transport
temporal response patterns
phasic
tonic
phasic-tonic
Adaption/Desensitisation
= change over time in the responsiveness to a constant stimulus --> net dynamic range of dose-response function higher
PKA (protein kinase A)
cyclic AMP dependent protein kinase (PKA or A-kinase)
• tetramer of 2 catalytic and 2 regulatory subunits
• each regulatory subunit with 2 cAMP-binding sites
• binding of 4 cAMP –> catalytic subunits dissociate & are active
• catalytic subunit = Ser/Thr kinase
Calcium ion influx - how are the channels opened?
voltage opened
store opened
seccond messenger opened
receptor opened
Cell Polarity
“persistent asymmetrical and ordered distribution of structures (or molecules) along an axis”
The basic tissue types in animals
- epithelia
- nervous tissue
- muscular tissue
- connective tissue
Epithelia
- line outer & inner sufaces of the body
- have two sides exposed to different environments
- are linked by junctional complexes
Molecular components of tight junctions
Claudin(s): homophilic interaction Occludin: homophilic interaction JAM = junctional adhesion molecule: member of Ig superfamily homophilic interaction
all contain
ZO-1, -2, -3: (zonula occludens) scaffolding proteins
zonula occludens contain which domains?
PDZ: binds other PDZ domains and Cterminal motifs –> protein complex
SH3: binds proline-rich motifs
GUK: protein binding
ABR: F actin binding
What are Cadherins?
- „calcium-dependent adhesion“
- cell adhesion molecules
- > 100 different cadherins by multiple genes & alternative RNA splicing
structure:
extracellular cadherin domains: Ca2+ binding –> forming homodimer
transmembrane domain
cytoplasmic tail: interaction with adopter and signaling proteins
Gap junctions
6x connexin = connexon
= hemichannel
pore Ø ̴1.4 nm
- passage of molecules up to 1000 Da (anorganic ions, incl. Ca2+; water; sugars; AA; metabolites; nucleotides incl. ATP & cAMP; IP3)
no passage of proteins
can be closed (regulated by e.g. Ca2+)
things enriched basolateral
Phosphatidylcholine
lipids: PIP2, PTEN
things enriched apical
Sphingomyelin
Glycolipids
Cholesterol
(lipids: PIP3, PI3 kinase)
Cell polarity is expressed at all hierarchical levels
- cell morphology
- organisation of the plasma membrane into domains that differ by molecular composition and function
- heterogeneous distribution of organelles in the cytoplasm
- polar organisation of the cytoskeleton (MTs, F-actin)
- heterogeneous distribution of proteins / mRNA in the cytoplasm
almost every cell in animals is polar
Basolateral sorting signals
–> identification and binding by clathrin-adaptor protein complex AP-1
4 SU (2 small and 2 big ones)
binding of AP-1 by clathrin –> vesicle formation
diffusional barriers
Ankrin
Spektrin
Na/K-ATPase
cell adhesion molecule
- endocytosis reduced
- proteins retained in the membrane
tight junctions hinder and prevent - what?
- tight junctions hinder exchange of membrane proteins between apical & basolateral domain
- tight junctions prevent diffusion of membrane lipids in the outer leaflet of the plasma membrane between apical & basolateral domain
