Cell-Cell Communication part I

Intercellular Communication

The process by which cells communicate with each other through various mechanisms.

3 general mechanisms of cell communication

1 Gap junctions

2 Direct Contact

3 Extracellular chemical messengers

Gap Junctions

Channels that bridge the cytoplasm of two cells, allowing direct passage of ions and small molecules.

Direct Contact

A mechanism of cell communication involving specific cell-surface markers that allow transient contact between two cells.

Extracellular Chemical Messengers

Molecules released by cells that communicate with other cells, classified into autocrine, paracrine, and endocrine signaling.

Extracellular Chemical Messengers Classes

1 Autocrine Signaling

2 Paracrine Signaling

3 Endocrine Signaling

Autocrine Signaling (Local Signaling)

A type of signaling where a cell releases a signaling molecule that binds to receptors on its own membrane.

Paracrine Signaling (Local Signaling)

Local diffusion of a chemical messenger that acts on nearby cells.

Endocrine Signaling (Long Distance Signaling)

Signaling molecules released into the blood that have long-range effects on cells remote from the site of release.

Receptor-Ligand Binding

The initial process in cell signaling where a signaling molecule binds to its specific receptor.

Signal Transduction

The process by which a receptor-ligand binding event leads to a series of cellular responses.

Ligand-Gated Ion Channels

Receptors that open in response to ligand binding, allowing ions to flow across the membrane.

G-Protein-Coupled Receptors

A large family of receptors that activate intracellular signaling pathways through G-proteins.

Enzyme-Linked Receptors

Receptors that are enzymes themselves, which become activated upon ligand binding.

Nuclear Receptors

Receptors that bind lipophilic hormones and regulate gene expression by interacting with DNA.

Second Messengers

Molecules that relay signals received at receptors on the cell surface to target molecules inside the cell.

Upregulation

The process of increasing the number of receptors on the cell surface, enhancing the cell's sensitivity to signaling molecules.

Downregulation

The process of decreasing the number of receptors on the cell surface, reducing the cell's sensitivity to signaling molecules.

Modificational Response

A rapid cellular response that occurs within milliseconds to minutes, such as secretion or changes in metabolism.

Transcriptional Response

A slower cellular response that involves gene expression and can take hours to develop.

Hormone Response Element (HRE)

A specific site on DNA where hormone-receptor complexes bind to regulate gene transcription.