Cell-Cell Communication - Exam 3 Flashcards
definition of a ligand
signaling molecule
permeable ligand characteristics
small, hydrophobic, lipophilic
example of permeable ligand
NO (vasodilation)
impermeable ligand characteristics
H2O soluble, polar, charged
example of impermeable ligand
growth factors/hormones like insulin
definition of a receptor
target cell, shape altered, specific
internal receptor characteristics
intracellular/cytoplasmic, hydrophobic ligands, binds to chromosomal DNA, gene expression
cell surface receptor characteristics
transmembrane, hydrophobic membrane spanning region, intracellular domain inside cell, signal transduction
examples of neurotransmitters
oxytocin, endorphin, dopamine, glutamate, glycine
examples of signal molecules in cell physiology
estradiol, thyroid hormones, testosterone, vitamin D3, retinoic acid, neurotransmitters, light- phototransduction, pressure- mechanotransduction, NO, CO, eicosanoids, growth factors/hormones like insulin
cell-cell signaling: gap junctions
passage of small molecules and ions like calcium
cell-cell signaling: tight junctions
seal neighboring epithelial cells i.e. lung
cell-cell signaling: adherens junctions
strong mechanical attachments i.e. cardiac muscle
cell-cell signaling: desmosomes
link intermediate filament cytoskeleton i.e. skin
cell itself signaling
autocrine- pain & inflammation
adjacent/nearby cell signaling
paracrine, synaptic signaling
distant cell signaling
endocrine
prostaglandins
paracrine & autocrine in nature, produced at man different sites in the body
ion-channel cell surface receptors
ligand-gated, transmembrane, Na, Ca, Mg, K, H, can pass through, nerve-muscle junction, neurons, glutamate & acetylcholine (cardiac/muscle cells, pancreatic acinar cells/exocytosis secretory granules)
intrinsic enzymatic activity cell surface receptors
convert GMP into cGTP, atrial naturetic protein
tyrosine kinase-linked cell surface receptors
cytokines, interferons, human growth factor
G protein cell surface receptors
second messenger, causes change in membrane potential, epinephrine, serotonin, angiotensin II, glucagon
examples of G protein cell surface receptors
rhodopsin, beta-adrenergic, frizzled
short term cell responses
ligand gated ion channels (ms) & GPCR (min)
long term cell responses
kinase linked receptors (hrs) & nuclear receptors (mins)
ionotropic membrane receptors
transmembrane: trigger short term and rapid responses & postsynaptic effects, cations & H2O can move through
ionotropic glutamate receptors
neuron burst/firing, NMDA (internal binding site for Mg2+)
metabotropic membrane receptors
linked to G proteins, activates a second messenger, longer response, glutamate receptors
examples of second messengers
cAMP, derivative of ATP, cGMP (visual reception in vertebrate eye) via rhodopsin, phospholipids, Ca2+, IP3, DAG
IP3 signaling
ADH, TRH, TSH, Angiotensin II, release of Ca2+ from intracellular stores by activating protein kinase C
PIP2 hydrolysis produces
DAG, IP3, PIP3 via phospholipase C, downstream of GPCR & receptor tyrosine kinase
cAMP signaling
synthesized by ATP via adenylyl cyclase; ACTH, TSH, LH, FSH, PTH, Calcitonin, glucagon, hCG, odorants, epinephrine, CREB
cAMP signaling activated by
PKA- activating/inhibiting protein activity, activating gene expression through transcription factors
intracellular receptors
phosphorylase kinase activates glycogen phosphorylase catalyzes breakdown of glycogen to glucose-1-phosphate
glycogen synthase
catalyzes glycogen synthesis
elevation of cAMP & activation of protein kinase A
blocks glycogen synthesis & stimulates glycogen breakdown
receptor inactivation done by
ligand degradation, endocytosis mediated receptor recycling, degradation of receptors by proteasomes, ligand sequestration by lysosomes
Ca2+ as a signaling molecule
signal transduction via activation of ion channels and indirect signal transduction pathways like G protein coupled receptors and ryanodine receptors
Calmodulin activated by Ca2+ binding
actin and myosin contraction
Ca2+ intracellular concentration =
lower than typical extracellular concentration, actively pumped from the cytosol to the extracellular space, ER, and mitochondria
Ca2+ signaling occurs when
cell stimulated to release Ca2+ from intracellular stores
Ca2+ homeostasis maintained by
calcium permeable channels, transporters, and ATPases
Ca2+ regulates what 3 things
(a)sexual development, circadian clock, protein folding
in electrically non-excitable cells like RBC,
influx of Ca2+ regulates exocytosis, enzyme control, gene regulation, cell growth, proliferation, apoptosis
depletion of Ca2+ from ER….
leads to Ca2+ entry from outside the cell by activation of SOCs, current created (CRAC), Orai1 & STIM1 activated (t lymphocytes)
Ca2+ physiologic functions
depolarization of the heart, antigen stimulation of immune cells, muscle contraction, cellular motility, fertilization, learning and memory, activation of isocitrate dehydrogenase
receptor mediated endocytosis
portion of plasma membrane invaginated, coated with clathrin, pinched off, forms an endosome
LDL receptors recycled
arrestin: receptor desensitization degradation recycling generate signalosomes which scaffold proteins to make downstream signaling events
