Cell Bio Exam 2 | Session 10 + 11

What is a signal/ligand

binds to receptor and is usually produced by another cell

is a signal usually soluble or insoluble

soluble

Allostery

molecule binds to a specific location on a protein (the allosteric site), causing a structural change that alters the protein's activity at a completely different, distant location

what are receptors

ligand binds to which causes it to change allosterically

what are signaling molecules

they are proteins that relay the signal from receptor to effectors

what are effectors

they are proteins that lead to direct changes in cell activty (usually last step)

what type of proteins is effectors usually (2)

enzymes, transcription factors

is the response in target cell usually fast or slow

either

what are the four types of cell signaling

1. endocrine signaling

2. paracrine signaling

3. autocrine signaling

4. signaling by plasma-membrane-attached proteins

what is endocrine signaling and what distance is it for, and what signaling molecule (type of protein) is involved (3)

• largest distance

• hormones that travel through blood stream to distant target cells

what is paracrine signaling, what distance is it for, and what signaling molecule (type of protein) is involved (3)

• short distance

• secretory vesicles take signaling molecules to local target cells

• neurotransmitters/growth

what is autocrine signaling, what distance is it for

• signaling molecules target itself

what is signaling by plasma-membrane-attached proteins, what distance

• signaling through adjacent touching cells though membrane attatched proteins

is a ligand specific to a single receptor?

no one ligand can bind to multiple receptors

is a receptor specific to a single effector?

no one receptor can be used for multiple effectors

what is the difference between hydrophobic signals and hydrophobic signals in terms of what receptor they bind to

• hydrophic can pass through the membrane and binds to cytosolic receptor (receptor in cytosol)

• hydrophillic binds to a cell-surface receptor

what is the difference between hydrophobic signals and hydrophobic signals in terms of signaling cascade

• hydrophic signals dont go through a signal transduction pathway

• hydrophillic signals go through multiple signal transduction proteins and secondry messengers

what is the difference between hydrophobic signals and hydrophobic signals in terms of how they affect the cell (2)

• hydrophobic impacts nucleus (gene expression)

• hydrophillic imacts nucleus and modification of cellular metabolism/movement

what types of molecules are hydrophillic signals (3)

1. small molecules

2. peptides

3. proteins

describe how receptors bind to their ligand in terms of specificity and affinity

• high specificity (binding site binds to one specific ligand)

• high affinity (binds tightly to the ligand)

what is binding affinity measured by

dissociation constant (Kd)

in the context of signaling what does lower kd mean vs higher kd

lower kd --> lower ligand conc needed to bind to 50% of receptors (higher binding affinity)

the sensitivity of a cell to a given signal is determined by (2)

1. binding affinity between signal and receptor (kd)

2. number of receptors

how are receptor levels regulated (4)

1. transcription

2. translation

3. post-translational processing

4. receptor-mediated endocytosis

which regulation method plays biggest role in how many proteins are made

transcription

what is a kinase

an enzyme that catalyzes the transfer of a phosphate group from ATP to a specified molecule.

what is a phosphatase

an enzyme that removes a phosphate from a protein

what is an activation loop and what activates it

activated by kinase through phosphorylation

what types of molecules are receptors usually (2)

phosphatases and kinases (GTPase)

how does receptors work with receptors specifically

can activate a receptor into either a kinase or phosphatase

what are the top numbers representing

increasing signal (ligand) concentration

what is stat5, akt, p42/p44

the proteins that are being phosphrylated by receptor/signal complex

what does anti-P vs anti mean

anti-P means binding of anibody to the phosphylated protein

anti means binding to just the protein regardless of if its phosphylated

interpret the meaning of this western blot

increasing signal conc increases the amount of phosphylated protein but the general amount of proteins stay the same

explain how:

• signal molecule

• receptor

• kinase

• kinase target

work to activate a kinase target (3 steps)

1. signal molecule binds to receptor

2. receptor is activated and recruites kinase enzyme

3. kinase binds to and phosphorylates kinase target (like stat5, akt, p42/p44)

what are heterotrimeric G-proteins made up of (3)

a, B, y subunit

what is monomeric g-protein made up of

Small, single-subunit protein

what is the difference between heterotrimeric and monomeric g-proteins

monomeric g-protein —> dont bind to receptor directly

heterotrimeric g-protein —> bind to receptor directly

how are g-proteins activated/deactivated

nucleotide exchange/gtp hydrolysis

How are kinase targets activated/deactivated vs. g-proteins (2 for each)

kinase: phosphylation/dephosphorylation

g-protein: nucleotide exchange/gtp hydrolysisw

what are examples of monomeric g-proteins (3)

ran, rabs, raswha

how is gef/gap associated with g-proteins and what type of g-protein uses it

only monomeric

gef —> nucleotide exchange (GDP —> GTP)

gap —> gtp hydrolysis (GTP —> GDP)

which g-protein needs receptor

heterotrimeric

what type of protein uses kinases vs which one uses gef/gap/receptors

kinase target —> kinases

g-protein —> gef/gap/receptors

explain how:

• signal molecule

• receptor

• gef/gap

work to activate a g-protein (3 steps) + bonus specify which g-protein

1. signal molecule binds to receptor (activates it)

2. receptor recruits gef/gap

3. gef/gap binds to monomeric g-protein and activates

explain how:

• signal molecule (specify name)

• receptor (specify name)

work to activate a g-protein (2steps) + bonus specify which g-protein

1. signal molecule binds to GPCR (receptor)

2. receptor is activated and stimulates nucleotide exchange/gtp hydrolysis on heteromeric gprotein

explain how this is working to show that rac-gtp binds to pak1 kinase better han rac-gdp

in the lysate #1 —> there is a weak band showing there is not really any pak1pbd

in lysate #2 —> strong band showing more binding which indicates rac-gtp is better at binding

what is a second messenger

signal molecules that aren’t proteins

what is the main example of a second messenger that we are discussing

cyclic AMP (cAMP)