Cell Signaling and Molecular Switches

Signaling

• Signaling is a term that describes the process of communication between cells.
• Signaling is critical for the proper functioning of all living organisms
• Signaling pathways are complex networks of interacting molecules that allow cells to respond to their environment
• A signaling pathway typically involves a series of steps, starting with the binding of a signal molecule to a receptor on the cell surface

Molecular switches

• Molecular switches are proteins that can be turned on or off by a signal molecule
• Molecular switches are often called kinases when they are on, and phosphatases when they are off
• Molecular switches play a key role in signaling pathways
• Molecular switches can act on the downstream components of signaling pathways

Downstream components

• Downstream components of Signaling pathways are the molecules that are affected by the signal molecule
• Downstream components of signaling pathways often include other proteins, but they can also include DNA or other molecules
• Downstream components act on the signal molecule
• Downstream components activate or repress the downstream components

Different forms of signaling

• Autocrine signaling is a form of signaling where a cell releases a signal molecule that binds to receptors on the same cell
• Paracrine signaling is a form of signaling where a cell releases a signal molecule that binds to receptors on nearby cells
• Endocrine signaling is a form of signaling where a cell releases a signal molecule that travels through the bloodstream to reach target cells

Signaling involving integrins

• Integrins are cell adhesion molecules that bind to the extracellular matrix
• Integrins can also act as receptors in signaling pathways
• Integrins play a key role in cell migration, growth, and differentiation

Signaling involving Ephrins

• Ephrins are a family of transmembrane proteins that act as ligands for Eph receptors
• Ephrins are involved in a wide range of developmental processes, including cell migration, axon guidance, and tissue patterning

Signaling involving steroids

• Steroid hormones are lipid-soluble molecules that can pass through the cell membrane
• Steroids can activate intracellular receptors
• Steroids promote activity related to development and metabolism
• Steroids are essential for the proper functioning of many tissues and organs

Signaling involving G protein-coupled receptors (GPCRs)

• GPCRs are a large family of cell surface receptors that are activated by a wide variety of ligands.
• GPCRs are involved in a wide range of processes, including sensory perception, neurotransmission, and hormone signaling.

Signaling involving protein tyrosine kinases (PTKs)

• PTKs are a family of enzymes that catalyze the transfer of phosphate groups from ATP to tyrosine residues on proteins.
• PTKs play a key role in many signaling pathways, including those involved in cell growth, differentiation, and survival.

Signaling involving receptor tyrosine kinases (RTKs)

• RTKs are a subfamily of PTKs that are activated by the binding of growth factors to their extracellular domains.
• RTKs play a key role in many signaling pathways, including those involved in cell growth, differentiation, and survival.

Signaling involving mitogen-activated protein kinases (MAPKs)

• MAPKs are protein kinases that are activated by a variety of stimuli, including growth factors, cytokines, and stress.
• MAPKs play a key role in many signaling pathways, including those involved in cell growth, differentiation, and survival.