cell bio final

Signal transduction

process where a signaling molecule from one cell triggers a specific response in a target cell

Ligand

signaling molecule that binds to a receptor to initiate a cellular response

Hydrophilic ligand

water-soluble signaling molecule that binds to cell surface receptors because it cannot cross the membrane

Hydrophobic ligand

lipid-soluble signaling molecule that crosses the membrane using carrier proteins or diffusion

Receptor

protein that specifically binds a ligand and initiates a cellular response

Signaling cell

cell that produces and releases a ligand

Responding cell

cell that has receptors for a ligand and reacts to it

Second messenger

intracellular molecule that relays signals from receptors to target molecules (e.g.

Effector protein

intracellular protein activated during signal transduction that produces a cellular response

Endocrine signaling

long-distance signaling via hormones traveling through the bloodstream

Paracrine signaling

local signaling affecting nearby cells

Autocrine signaling

signaling where a cell targets itself

Plasma membrane-attached signaling

signaling via membrane-bound ligands affecting adjacent cells

Lipophilic hormones

hydrophobic hormones that diffuse through membranes and bind intracellular receptors

Heterodimeric nuclear receptors

receptors located in the nucleus that regulate gene expression upon ligand binding

Peptide hormones

hydrophilic signaling molecules made of amino acids (e.g.

Small charged molecules

hydrophilic signaling molecules like epinephrine and histamine

Receptor dimerization

process where two receptors bind together after ligand binding to activate signaling

Protein kinases

enzymes that add phosphate groups to proteins to regulate activity

Phosphatases

enzymes that remove phosphate groups from proteins

GTP-binding proteins

molecular switches that bind GTP to become active

Adapter proteins

proteins that link receptors to downstream signaling proteins without enzymatic activity

SH2 domain

protein domain that binds phosphorylated tyrosine residues

SH3 domain

protein domain that binds proline-rich sequences

PTB domain

protein domain that binds phosphotyrosine residues

Dissociation constant (Kd)

measure of receptor-ligand binding affinity (lower Kd = higher affinity)

Agonist

molecule that activates a receptor to produce a response

Antagonist

molecule that binds a receptor but blocks activation

Binding assay

experimental method to measure receptor-ligand interactions

GPCR (G-protein-coupled receptor)

seven-pass membrane receptor that activates G proteins

G protein

trimeric protein (alpha

GDP

inactive form bound to G protein alpha subunit

GTP

active form bound to G protein alpha subunit

Gs protein

G protein that stimulates adenylate cyclase

Gi protein

G protein that inhibits adenylate cyclase

Gq protein

G protein that activates phospholipase C

Adenylate cyclase

enzyme that converts ATP to cAMP

cAMP

second messenger that activates protein kinase A

Protein kinase A (PKA)

kinase activated by cAMP that phosphorylates target proteins

Phospholipase C (PLC)

enzyme that cleaves PIP2 into IP3 and DAG

PIP2

membrane phospholipid cleaved into IP3 and DAG

IP3

second messenger that releases calcium from the ER

DAG

membrane-bound second messenger that activates PKC

Protein kinase C (PKC)

kinase activated by DAG and calcium

Receptor tyrosine kinase (RTK)

membrane receptor with intrinsic kinase activity

RTK dimerization

pairing of two RTKs upon ligand binding

Cross-phosphorylation

RTKs phosphorylate each other to activate signaling

MAPK pathway

signaling cascade involved in gene expression

GRB2

adapter protein linking RTKs to SOS

SOS

guanine nucleotide exchange factor that activates Ras

Ras

small G protein involved in cell signaling and cancer

GEF

protein that activates G proteins by exchanging GDP for GTP

GAP

protein that inactivates G proteins by stimulating GTP hydrolysis

Raf

kinase activated by Ras in MAPK pathway

MEK

kinase activated by Raf

MAPK (ERK)

kinase that regulates gene expression

PI3K pathway

signaling pathway involved in growth and survival

PI3K

enzyme that converts PIP2 to PIP3

PIP3

lipid that recruits AKT to the membrane

AKT (PKB)

kinase that promotes survival and growth

PDK1/PDK2

kinases that activate AKT

mTOR pathway

pathway regulating cell growth and metabolism

Cell cycle

series of events leading to cell division

Interphase

phase where the cell grows and replicates DNA

Mitosis

phase where the cell divides

G1 phase

cell growth and preparation for DNA replication

S phase

DNA replication phase

G2 phase

preparation for mitosis and error checking

M phase

mitosis and cytokinesis

Checkpoint

control point ensuring proper cell cycle progression

pRB

tumor suppressor protein that inhibits E2F

E2F

transcription factor required for S phase entry

Cyclin D

protein that phosphorylates pRB to allow cell cycle progression

Cyclin E

protein required for DNA replication initiation

Cyclin B/CDK1 complex

complex that controls entry into mitosis

p53

tumor suppressor that halts cell cycle and induces repair or apoptosis

p21

inhibitor of cyclin/CDK complexes activated by p53

ATM/ATR

proteins that detect DNA damage

Chk2

kinase that activates p53

Apoptosis

programmed cell death

Caspase 3

enzyme involved in apoptosis execution

Cytochrome C

mitochondrial protein that triggers apoptosis when released

APC (anaphase promoting complex)

E3 ubiquitin ligase regulating mitosis

Ubiquitination

process marking proteins for degradation

Securin

protein that inhibits separase

Separase

enzyme that separates sister chromatids

Centromere

region where sister chromatids are joined

Spindle fibers

structures that pull chromatids apart

Prophase

stage where chromosomes condense and nuclear envelope breaks down

Metaphase

stage where chromosomes align at the metaphase plate

Anaphase

stage where sister chromatids separate

Telophase

stage where nuclear membranes reform

Cytokinesis

division of the cytoplasm

BRCA1

tumor suppressor gene involved in DNA repair

BRCA2

tumor suppressor gene involved in DNA repair

HBOC syndrome

hereditary breast and ovarian cancer syndrome

Autosomal dominant inheritance

inheritance pattern where one mutated allele causes disease