"In biology, cell signaling (cell signalling in British English) or cell communication is the ability of a cell to receive, process, and transmit signals with its environment and with itself."
The study of the various signaling pathways that cells use to communicate with each other and respond to their environment.
Receptor Proteins: These are membrane bound proteins that receive signals from outside the cell and initiate intracellular signaling events.
Ligands: These are molecules that bind to receptor proteins and initiate signaling events.
Signal Transduction: This is the process by which extracellular signals are converted into intracellular signals, leading to cellular responses.
Second Messenger Pathways: These are signaling pathways that involve the generation of intracellular signaling molecules, such as cAMP, IP3, and DAG.
Protein Kinases and Phosphatases: These are enzymes that add or remove phosphate groups from specific proteins, thereby regulating their activity and function.
G-Proteins: These are a family of proteins that interact with receptor proteins and transmit signals from the cell surface to intracellular signaling cascades.
Calcium Signaling: This is the communication process between calcium ions and proteins in the cytoplasm that regulate various cellular activities.
Receptor Tyrosine Kinases: These are a class of membrane-bound receptors that possess an intracellular tyrosine kinase domain, which activates downstream signaling pathways.
Mitogen-Activated Protein Kinases (MAPKs): These are intracellular signaling molecules involved in the control of cell proliferation, differentiation, survival, and death.
Transcription Factors: These are proteins that bind to DNA and regulate the expression of specific genes, leading to changes in cellular phenotype and function.
Protein-Protein Interactions: These are interactions between proteins that are essential for the assembly of signaling complexes and the propagation of signaling events.
Cytokines: These are signaling molecules involved in the regulation of the immune system, inflammation, and other physiological processes.
Apoptosis: This is the process of programmed cell death, which is regulated by various signaling pathways and plays a crucial role in normal development and tissue homeostasis.
Autophagy: This is the process of cellular self-eating, which is important for the maintenance of cellular homeostasis and survival under stress conditions.
Epigenetic Regulation: This is the process by which modifications of chromatin structure and DNA methylation alter gene expression and contribute to cellular differentiation and function.
Endocrine signaling: Hormonal signals released by endocrine glands that travel through the bloodstream to target cells throughout the body.
Paracrine signaling: Short-range signaling molecules that target nearby cells, often diffusing through extracellular space.
Autocrine signaling: Signaling molecules that target the same cell that released them, allowing the cell to change its own behavior or maintain homeostasis.
Juxtacrine signaling: Signaling between adjacent cells that requires physical contact between the two cells.
Intracrine signaling: Signaling molecules that remain within the cell and affect intracellular signaling pathways.
Neurotransmitter signaling: Chemical signals released by neurons that travel across synapses to target cells, triggering a response.
Gap junction signaling: Direct transfer of small molecules and ions between adjacent cells via gap junctions.
G-protein coupled receptor signaling: Signaling pathway where a ligand binds to a transmembrane receptor, activating a G-protein to initiate a downstream signaling cascade.
Receptor tyrosine kinase signaling: Signaling pathway where a ligand binds to a receptor tyrosine kinase, leading to the activation of downstream signaling pathways.
Ion channel signaling: Signaling pathway where a ligand causes a conformational change in an ion channel, allowing ions to flow into or out of the cell.
Growth factor signaling: Signaling pathway where a ligand binds to a receptor and promotes cellular growth and proliferation.
Cytokine signaling: Signaling pathway where cytokines activate intracellular signaling pathways, promoting immune responses or other cellular processes.
Steroid hormone signaling: Signaling pathway where lipid-soluble steroid hormones bind to intracellular receptors and regulate gene expression.
Nitric oxide signaling: Signaling pathway where nitric oxide acts as a signaling molecule, modulating smooth muscle relaxation, neurotransmission, and other processes.
Redox signaling: Signaling pathway where reactive oxygen species (ROS) and reactive nitrogen species (RNS) act as signaling molecules to regulate cellular processes.
"Signals that originate from outside a cell (or extracellular signals) can be physical agents like mechanical pressure, voltage, temperature, light, or chemical signals (e.g., small molecules, peptides, or gas)."
"Cell signaling can occur over short or long distances, and as a result can be classified as autocrine, juxtacrine, intracrine, paracrine, or endocrine."
"Signaling molecules can be synthesized from various biosynthetic pathways and released through passive or active transports, or even from cell damage."
"Receptors are generally proteins located on the cell surface or within the interior of the cell such as the cytoplasm, organelles, and nucleus."
"Cell surface receptors usually bind with extracellular signals (or ligands), which causes a conformational change in the receptor that leads it to initiate enzymic activity, or to open or close ion channel activity."
"Some receptors do not contain enzymatic or channel-like domains but are instead linked to enzymes or transporters."
"Other intracellular receptors like nuclear receptors have a different mechanism such as changing their DNA binding properties and cellular localization to the nucleus."
"Signal transduction begins with the transformation (or transduction) of a signal into a chemical one, which can directly activate an ion channel (ligand-gated ion channel) or initiate a second messenger system cascade that propagates the signal through the cell."
"Second messenger systems can amplify a signal, in which activation of a few receptors results in multiple secondary messengers being activated, thereby amplifying the initial signal (the first messenger)."
"The downstream effects of these signaling pathways may include additional enzymatic activities such as proteolytic cleavage, phosphorylation, methylation, and ubiquitinylation."
"Each cell is programmed to respond to specific extracellular signal molecules, and is the basis of development, tissue repair, immunity, and homeostasis."
"Errors in signaling interactions may cause diseases such as cancer, autoimmunity, and diabetes." Please note that the provided quotes directly answer the study questions and are taken from the original paragraph.