Chemical signaling
Release of chemical molecules into extracellular fluid or diffused inside of the cells
- Autocrine signaling
Cell respond to molecules they produce themselves - Gap junctions
From direct cytoplasmic connections between adjacent cells - Paracrine signaling
Cell respond to molecules they produce themselves - Endocrine signaling
Secretion of molecules(hormones) into the bloodstream and travel relatively long distances to reach target cells
Electrical signaling
Conduction of an electrical current between connected cells
e.g.: neurotranmission
Mechanical signaling
Direct communication between cells with help of surface proteins that initiates specific biochemical reactions in the participating cells
e.g.: juxtacrine signaling
Cell surface receptors
Converting an exreacellular signaling(water-soluble) into an intracellular signal
Ion channels
Voltage-gated ion channels
Respond to changes in membrane potential with conformational changes that lead to opening or close channel pore
e.g.: Sodium, potassium and calcium channels
Extracellular ligand-gated channels
Similar to other ion channels BUT incorporating a ligand-binding (receptor) site, usually in the extracellular domain
e.g.: gamma-aminobutyric acid (GABA), Glycine receptor channels
Intracellular ligand-gated channels
Gated by ligands inside the cell
e.g.: The cystic fibrosis transmembrane conductance regulator (CFTR) channel
G protein-linked receptors and signaling transduction
- Recognition
- Conformational change
- G protein activation
Enzyme linked receptor
Intracellular receptors
Lipid-soluble (hydrophobic) molecules diffuse across plasma membrane and interact with intracellular receptors to form a complex in the cytoplasm.
The complex act on the DNA and regulate gene expression.
Stages of chemical signaling(hydrophilic molecules)
- Reception: Signal molecule (ligand) serve as first messenger that binds to receptor
- Transduction: The receptor in turn activates one or more intracellular signal molecules (second messenger molecules)
- Response: The second messenger molecules initiates synthesis of target proteins or modifies existing target protein to create response