Chapter 17 Flashcards
direct interaction of a cell with its neighbor, (e.g., via integrins and cadherins).
Direct cell-cell signaling
three categories are based on the distance over which signals are transmitted.
Signaling by secreted molecules
Secreted by specialized endocrine cells and carried through the circulation to target cells at distant body sites. Example: estrogen
Endocrine signaling
Released by one cell act on neighboring target cells. Example: neurotransmitters
Paracrine signaling
Cells respond to signaling molecules that they themselves produce.
Example: T lymphocytes respond to antigens by making a growth factor that drives their own proliferation.
Autocrine signaling
respond to small hydrophobic molecules that can diffuse across the plasma membrane.
Intracellular receptors
Intracellular receptors examples
Steroid hormones, thyroid hormone, vitamin D3, and retinoic acid.
Steroid hormones are synthesized from:
cholesterol
Testosterone, estrogen, and progesterone are the
sex steroids
Corticosteroids from the adrenal gland:
(2 types)
Glucocorticoids
Mineralocorticoids
an insect hormone that triggers metamorphosis of larvae to adults.
Ecdysone
plant steroid hormones that control several processes, including cell growth and differentiation.
Brassinosteroids
synthesized from tyrosine in the thyroid gland; important in development and metabolism.
Thyroid hormone
regulates Ca2+ metabolism and bone growth.
Vitamin D3
synthesized from vitamin A; important in vertebrate development.
Retinoic acid
Glucocorticoid receptor is bound to _____ chaperones in the absence of hormone.
Hsp90
associated with a corepressor complex and represses transcription of target genes in the absence of a hormone
thyroid hormone receptor
a paracrine signaling molecule in the nervous, immune, and circulatory systems.
Nitric oxide
_____ induces muscle cell relaxation and blood vessel dilation.
cGMP
Many neurotransmitter receptors are ______ ion channels.
ligand-gated
Other neurotransmitter receptors are coupled to __ proteins
G
Peptide signaling molecules include (3 things)
- peptide hormones, 2. neuropeptides, and 3. polypeptide growth factors.
include insulin, glucagon, and pituitary gland hormones (e.g., growth hormone, follicle-stimulating hormone, prolactin).
Peptide hormones
act as neurotransmitters and as neurohormones—natural analgesics that decrease pain responses; they bind to the same receptors on brain cells as morphine does.
Enkephalins and endorphins
a member of the neurotrophin family that regulates development and survival of neurons.
Nerve growth factor
stimulates cell proliferation. It is the prototype for the study of growth factors.
Epidermal growth factor
stored in blood platelets and released during blood clotting at the site of a wound.
Platelet-derived growth factor
regulate development and differentiation of blood cells and activities of lymphocytes during the immune response.
Cytokines
remain associated with the plasma membrane and function as signaling molecules in direct cell-cell interactions.
Membrane-anchored growth factors
The surface receptors regulate intracellular enzymes, which then transmit signals from the receptor to a series of additional intracellular targets.
Intracellular signal transduction
the largest family of cell surface receptors
G protein-coupled receptors
synthesizes cAMP
adenylyl cyclase
G proteins have three subunits designated α, β, and γ.
They are called:
heterotrimeric G proteins.
α and βγ complex then ______ from the receptor and interact with their targets.
dissociate
In 1958 Sutherland discovered that epinephrine action was mediated by an increase in cyclic AMP (cAMP), leading to the concept of cAMP as a
second messenger.
cAMP is degraded to _____ by cAMP phosphodiesterase.
AMP
cAMP effects are mediated by cAMP-dependent protein kinase, or:
protein kinase A.
In many animal cells, increases in cAMP activate transcription of genes that have a regulatory sequence called
cAMP response element (CRE).
The free catalytic subunit of protein kinase A goes to the nucleus and phosphorylates transcription factor
CREB
Phosphorylation of CREB leads to recruitment of
coactivators
phosphorylate their substrates on tyrosine residues.
tyrosine kinases
Receptor tyrosine kinases includes the receptors for most ________ growth factors.
polypeptide
Ligand binding induces _________ of receptors, and cross-phosphorylation of associated nonreceptor tyrosine kinases.
dimerization
a cascade of protein kinases that is highly conserved in evolution, found in all eukaryotic cells.
MAP kinase pathway
MAP kinases initially found in mammalian cells belong to the _____ family.
ERK (extracellular signal-regulated kinase)
The role of ERK signaling emerged from studies of _____ proteins
Ras
Ras is activated by _____ that stimulate exchange of GDP for GTP.
GEFs
A primary response to growth factor stimulation is rapid transcription of
immediate-early genes.
Specificity of MAP kinase signaling is maintained partly by physical association on
scaffold proteins.
PIP2 is phosphorylated PI to yield the second messenger _____
PIP3
