ILA Intracellular Signaling (Sayner)

Question 1

Signal Transduction

Answer 1

the process of converting a signal from outside of the cell into a functional change inside the cell

Question 2

Biochemical signal

Answer 2

released by signaling cell and recognized by target cell

is a ligand

binds to receptor protein → activates series of intracellular signaling proteins → effector proteins alter cell behavior

Question 3

autocrine

Answer 3

signaling cell secretes a signaling molecule that it also responds to

Question 4

paracrine

Answer 4

signaling molecule is released into the extracellular space and acts locally

short half life

Question 5

endocrine

Answer 5

released into blood and reach distant targets throughout body

Question 6

Group 1 hormones

Answer 6

• interact with intracellular receptors
• hydrophobic
• bound to carrier protein in blood
• Ex: steroids

Question 7

Group II hormones

Answer 7

• hydrophilic (can travel thru blood)
• interact with plasma membrane bound receptors
• Ex: amines, small peptides, proteins

Question 8

Intracellular receptors in cytoplasm

Answer 8

hormone enters cell → binds to receptor → conformational change → promotes dissociation of protein complex → ligand bound receptor moves into the nucleus and binds to DNA to initiate gene transcription

Question 9

intracellular receptors in the nucleus

Answer 9

hormone enters nucleus → binds to receptor associated with response element on DNA → conformational receptor change → dissociation of repressor → gene transcription initiated

Question 10

Cell surface receptor - ion channel coupled

Answer 10

Rapid signaling

ligand binds to receptor, which is an ion channel → ion channel opens and ions enter following concentration gradient

Question 11

cell surface receptors- G protein coupled receptors

Answer 11

transmembrane spanning

a trimeric GTP-binding protein mediates the interaction between the activated receptor and the target protein

Question 12

cell surface receptors- enzyme coupled receptors

Answer 12

binding of signaling molecule → dimerization of receptor → cytosolic domains of receptor brought together → intrinsic enzyme activity/associated with protein with enzymatic activity (protein kinases)

Question 13

Protein kinase

Answer 13

phosphorylates hydroxyl → turns ON

can be serine/threonine or tyrosine

Question 14

protein phosphatase

Answer 14

removes phosphates → turns OFF

Question 15

GTP-binding proteins

Answer 15

have very slow intrinsic GTP-ase activity (turn themselves off)

trimeric: G-proteins, relay signals from GPCR
monomeric: small monomeric GTP-ases

Question 16

GEFS

Answer 16

promote release of bound GDP, allowing GTP to bind → ON

Question 17

GAPs

Answer 17

hydrolyze GTP to GDP → OFF

Question 18

Signaling specificity

Answer 18

• high affinity
• threshold level of activation
• scaffolding proteins bring components of signaling pathways into close proximity