BIOL408 Unit 3- cell signaling intro

what are the two kinds of signaling receptors?

intracellular and cell surface receptors

intracellular signaling receptors

receptors found within the cell, either cytoplasm or nuclear

cell surface receptors

receptors found on the plasma membrane

how are intracellular receptors activated?

when a ligand changes the transcription of specific genes

how do cell surface receptors activate signals?

initiate signal transduction cascades that alter gene expression, metabolism or structure

what are the 3 types of cell surface receptors?

ion channels, GPCRs, and enzyme-linked receptors

signal transduction cascades

series of chemical reactions that allow cells to react and respond to changes in the environment

what happens when there are multiple signals read by a cell?

the cell can respond to more than one signal at a time, combination determines fate

what are the main two ways signals are transmitted?

enzymatic activities and non-covalent interactions

enzymatic activities that transmit signals

GTP binding proteins and phosphorylation

phosphorylation kinases

hydrolyze ATP to ADP and adds removed phosphate to the protein

phosphatase

dephosphorylates proteins

what type of binding occurs during phosphorylation?

covalent

GEF turns proteins

on

GAP turns proteins

off

binding motifs

specific AA sequences that influence binding with other proteins

what are 3 common binding motifs?

PH, PTB/SH2, and SH3

PH binding motif

bind to phosphorylated inositol phospholipids (PIP)

PTB/SH2 binding motif

bind to phosphorylated tyrosine residues

SH3 binding motif

bind to proline-rich motifs

signalosomes

protein complexes formed by binding motifs that increase signaling activities

in what way do certain signal transduction pathways imitate epistasis?

the alteration of one signaling protein may impact functions that are downstream of the signal cascade

what are two kinds of protein-protein interaction assays?

co-immunoprecipitation and yeast two-hybrid assay

what is the purpose of protein-protein interaction assays

to identify one protein and look for the interacting proteins

co-immunoprecipitation

protein specific antibodies that pull down specific protein interactions

yeast two-hybrid assay

protein-fragment complementation assay, done in yeast

what are the two levels that signaling termination can occur on?

the signal molecule level and the receptor level

how can signals be terminated on the signal molecule level?

dephosphorylation, GAP hydrolysis, and ubiquitination

desensitization

inactivation or inhibition of receptors

B-arrestin

protein that binds to phosphorylated receptors and inhibits interaction and initiates endocytosis

what proteins does B-arrestin bind to?

G proteins and RTKs

how does B-arrestin initiate endocytosis?

it recruits clathrin coated vesicles to remove proteins from the membrane

sequestration

the transport of inhibited molecules to an endosome

what are the three locations in an endosome?

early endosome, recycling endosome, and the late endosome

early endosome

the destination of active receptors to be inhibited

what happens to proteins after they are brought to the early endosome?

they are either sent to the recycling endosome or the late endosome for degradation

recycling endosome

recycles proteins by re-embedding them into the membrane

late endosome

fuse with lysosomes to bring proteins to degradation