Chapter 15: Cell Signaling Flashcards
What are the 7 different types of cell signalling molecules?
- proteins/peptides
- nucleotides
- steroids
- retinoids
- fatty acids
- nitric oxide
- ions
What are two methods of signal release from the signaling cell?
- membrane expression
- exocytosis secretion
Intracellular receptors on the target cell are primarily used for what type of signals?
lipid signals
what type of receptor on the target cell is used for most other signals?
surface receptors
What are the 5 types of cell signaling?
- contact-dependent
- paracrine
- autocrine
- endocrine
- synaptic
contact-dependent signaling is required in what scenarios?
- development
- immune response
contact-dependent signaling usually involves what type of signal?
membrane-associated/bound signal molecules
this type of cell signaling occurs on a small scale between intermediate cells with the target recptor
paracrine
this type of cell signaling is responsible for the “community effect” where a certain cell type secretes a signal that it has receptors for itself
autocrine
this type of cell signaling is predominant in cancer cells to ensure cell survival and rapid growth
autocrine signaling
type of cell signaling that is very large scale; signal is released into the blood and transported to widely-spread target cells
endocine
this type of cell signaling occurs only between neuronal cells; electrical signals stimulate NTM release to next cell
synaptic signaling
fast cell signals usually involve what responses?
altered protein function, channel opening, activation (“on”/”off”)
slow cell signals usually involve what responses?
gene expression alteration
what is the time frame of fast cell signaling?
seconds to minutes
what is the time frame of slow cell signaling?
minutes to hours
these are specialized cell-cell junctions that connects 2 cells; usually involves one continuous pathway/channel
gap junctions
about how big are gap junctions between cells?
2-4 nm
what types of molecules do gap junctions transfer?
secondary signals & small molecule signals; NO proteins
What are the 4 different outcomes of survivability-related signals
- survive
- grow + divide
- differentiate
- death
What signals are live cells always receiving?
survival signals to counteract death signals
What is the ACh response in skeletal muscle cells?
muscle contraction
What is the ACh response in pacemaker cells (i.e. SA node)
Slowing of spontaneous firing/depolarization
What is the ACh response in salivary cells?
sectretion
What are the three major classes of receptors?
- ion channels
- G protein coupled
- enzyme linked
This receptor type relies on surface chemistry reactions to create a conformational change of channel proteins
ion-gated-coupled receptors
What are the results of ion-gated-coupled receptors?
conformational change allows passive diffusion of ions in the presence of a gradient
most medicines work on this receptor pathway
G protein-coupled receptors
What are the three biggest components of the G protein-coupled receptors?
- receptor
- G protein
- enzyme
Most G protein receptors are found in what type of physiological functions?
sensory
What feature of G protein receptors allows for quick enzyme interactions?
membrane association of relevant proteins
about how many known G protein receptors are orphaned?
~120
This type of receptor occurs when a signal molecule interacts with a receptor to produce activitty
enzyme coupled receptors
What two types of enzyme activity can result from enzyme coupled receptors?
- inherent
- associated
What is inherent enzyme activity of an enzyme-coupled receptor?
the receptor enzyme produces activity
What is associated enzyme activity of an enzyme-coupled receptor?
the activated receptor results in the activity of an enzyme not bound to the receptor
kinase cascades are an example of what type of receptor?
enzyme-coupled receptors
this subgroup of enzyme coupled receptors have many steps that accumulate the response to a small amount of signal
cascades
What is a benefit of the many steps of cascading enzyme activity?
allows for multiple points of regulation
What is the purpose of scaffolding proteins in cascades?
anchor substrates and products near each other for quick reactions
What are the two phosphorylation systems?
- signaling by phosphorylation
- signaling by GTP binding
what are two examples of phosphorylation-based signals?
- kinases (adds Pi)
- phosphatases (removes Pi)
This term describes the idea that cell signal response depends on the sum total of the signals received
signal integration
What are 5 methods of cell-to-ligand signal desensitization?
- receptor sequesteration
- receptor down-regulation
- receptor inactivation
- signal protein inactivation
- inhibitory protein production
The Ras protein-involving pathway is an example of what?
Receptor tyrosine-kinase survival signal pathway
This is a monomeric GTPase protein found in all examined cells that signals to the nucleus to induce cell proliferation
Ras protein
What happens when the Ras protein is mutated?
loss of GTP hydrolysis activity –> always “on” –> encourages cell proliferation –> cancer dev
About what percentage of all human tumors have a mutated Ras protein/gene?
30%
This protein allows GDP to unbind from the Ras GTPase and be replaced with GTP
GEF (Guanine Exchange Factor)
This protein is responsible for removing the Pi from the GTP bound to Ras GTPase in its “on” state
GAP (GTPase activating protein)
What is the purpose of the SH2 domain in the Ras-mediated pathway
Recognizes phosphorylated-tyrosines on and activated RTK (receptor tyr-kinase)
Where is the SH2 domain found in the Ras-mediated pathway?
on the Grb2 protein
This protein has both SH2 and SH3 (2) domains for specificity
Grb2 adaptor protein
This protein transduces the signal from the activated RTK and exchanges GDP from Ras protein for GTP
Ras-GEF (Sos)
This protein receives an activation signal from the active Ras protein to begin cascade
MAP kinase3 (Raf)
This protein receives signal from activated Raf kinase protein to continue cascade
MAP kinase2 (Mek)
This protein receives signal from the activated Mek protein to further phosphorylate downstream proteins
MAP kinase (Erk)
What are the 4 proteins that MAP kinase (Erk) phosphorylates
- protein X
- protein Y
- transcription regulation protein A
- transcription regulation protein B
