Cell Communication - Chapter 16

Flashcards about Cell Communication

Endocrine

Long-range signaling using hormones.

Paracrine

Short-range signaling using ligands and receptors.

Contact-dependent

Signaling that requires direct cell-to-cell contact.

Steroid Hormones

Examples include testosterone, estradiol, and cortisol.

Nitric Oxide (NO)

A gaseous signaling molecule involved in vasodilation and vasoconstriction.

GPCR (G Protein-Coupled Receptor)

Receptor that activates G proteins.

RTK (Receptor Tyrosine Kinase)

Receptor that phosphorylates tyrosine residues.

Guanylyl cyclase and Adenylyl cyclase

Enzymes that produce cGMP and cAMP respectively.

Speed of Signaling

Signaling can be fast or slow, depending on whether changes involve proteins already present or changes in transcription.

Receptor Location

Receptors can be located on the outside of cells or in the cytoplasm, depending on the ligand's ability to cross the plasma membrane.

Receptor Activation

Receptor and signaling protein activation is caused by a conformational change or a modification to amino acid side chains.

Signaling Molecules

Signaling molecules can be small or large, and they need to bind to and act upon each other. Concentration relative to Kd affects binding.

Termination of Signaling

Signaling stops when cGMP/cAMP is degraded, G proteins hydrolyze GTP to GDP, and phosphatases dephosphorylate serine, threonine, and tyrosine.

Endocrine Signaling

Signaling method involving a hormone traveling through the bloodstream to a distant target cell.

Paracrine Signaling

Signaling method where a cell releases a local mediator that affects target cells in close proximity.

Neuronal Signaling

Signaling method using neurons to transmit signals across synapses using neurotransmitters.

Contact-Dependent Signaling

Signaling method requiring direct contact between a signaling cell and a target cell via membrane-bound signal molecules and receptors.

Cell Surface Receptors

Hydrophilic ligands bind to these receptors.

Intracellular Receptors

Hydrophobic or gaseous molecules bind to these receptors.

Steroid Hormones

These hormones, derived from cholesterol, can easily pass through the plasma membrane.

Nitric Oxide

It diffuses to smooth muscle cells and activates guanylyl cyclase, leading to smooth muscle relaxation.

Sildenafil

It inhibits PDE5, preventing the degradation of cGMP and leading to vasodilation.

Ion Channel Activation

Extracellular signal molecule binds to the channel, causing a conformational change.

Common Signaling Systems

Serine/threonine or tyrosine phosphorylation by a kinase, or GTP-binding proteins.

G alpha subunit

It activates adenylyl cyclase.

Beta/gamma subunit

It activates the potassium channel.

Adenylyl Cyclase

It makes cAMP from ATP.

cAMP phosphodiesterase

It breaks down cAMP into AMP.

Adrenaline

It activates adenylyl cyclase, leading to cAMP production.

IP3 and DAG

PLC cuts PIP3 into these two molecules

Ca++

What does IP3 cause to be released from the ER?

Protein Kinase C (PKC)

What does DAG activate?

Calmodulin

Calcium-dependent signaling molecule activated in the fertilized egg.

Receptor Tyrosine Kinase Activation

The cytoplasmic tail of the ligand bound activated receptor changes shape and activates the kinase.

MAPK

Activated Ras activates a MAPKKK, which activates MAPKK, which activates this molecule.

Bad

Activated Akt phosphorylates this pro-death protein.

c-kit (RTK)

Constitutively phosphorylated in the absence of its ligand SCF in mast cell tumors.