Cell Signaling

Signal/Ligand

External factor triggering a cellular response

Receptor

A protein that binds the signal and alters its activity

Signaling Intermediates

Molecules transmitting the signal inside the cell.

Effectors

The molecule that directly mediates the cell's response.

Kinase

An enzyme that adds phosphates groups to proteins, activating, or inactivating them

Phosphates

Removes phosphate groups from proteins.

Phosphorylation

The addition of a phosphate group to a molecule, altering its activity.

Steroid Hormones

Lipid molecules that pass through the cell membrane and bind intracellular receptors.

Receptor-Kinase

A receptor that activates kinase activity upon ligand binding.

Ras

A G-protein controlled by GTP/GDP binding.

MAPK, MAPKK, MAPKKK

Kinases involved in the MAPK signaling cascade.

MAPK pathway components

• Signal EGF

• Receptor EDFR

• Signaling Intermediate : RAS, MAPKKK,

Why do cells need signaling

to receive and respond to information from their environment, allowing them to coordinate their activities and maintain homeostasis, crucial for survival and function, especially in multicellular organisms

lipid soluble/insoluble signal

Lipid-soluble signals, like steroid hormones, can directly cross cell membranes and bind to intracellular receptors, while lipid-insoluble signals, like peptide hormones, require surface receptors and initiate signaling cascades via second messengers

primary/secondary messenger

primary messengers (like hormones or neurotransmitters) initiate signals by binding to cell surface receptors,

while secondary messengers (like cAMP or calcium) relay the signal inside the cell, triggering downstream responses. 

Dimerization

2 polypeptides come together

why does signal transduction go through so many complicated steps

because of several important biological reasons:

1)Signal Amplification: increase # of activated cell components

2)Signal Branching: one signal activates multiple cellular responses

3) Signal Integration: 1 cellular response is controlled by multiple signals

What would happen to MAPK signaling if you injected the cells with a nonhydrolyzable form of GTP?      

Ras would be active all the time

cell surface receptor vs Intercellular receptor

Cell surface receptors are transmembrane proteins embedded in the cell membrane that bind to extracellular ligands

Intracellular receptors are located inside the cell and bind to ligands that have diffused across the membrane

Steroid hormone receptor

transcription factors that can directly bind to enhancer elements in DNA to regulate transcription.

receptor kinase

Involved in cell signaling, not direct transcription regulation.

reporter gene

It's used experimentally to track activity but doesn't bind to enhancer elements itself.

transmembrane receptor

cell surface receptors embedded in the plasma membrane that span the entire membrane, receiving extracellular signals and initiating intracellular responses through ligand binding and signal transduction