Cell Signaling Overview and Types

Cells respond to external stimuli by activating specific signaling pathways.

Signaling molecules can be classified based on the distance they travel: Endocrine (long distance, hormones in bloodstream), Paracrine (short distance, local effects), Autocrine (self-signaling).

Cell signaling is crucial for regulating cell growth and division, affecting virtually every aspect of cell structure and function.

Cells can only respond to signals if they possess a receptor for that specific signaling molecule.

Steroid hormone receptors are intracellular receptors that bind to steroid hormones like cortisol and estradiol. These receptors are part of the nuclear receptor superfamily which acts as transcription factors.

A class of proteins that can bind to specific DNA sequences and regulate gene expression. They contain domains for ligand binding, DNA binding, and transcriptional activation.

A type of signaling pathway where the signaling molecule enters the cell and binds to an intracellular receptor. This complex then acts as a transcription factor, directly regulating gene expression.

Enzymes that add phosphate groups to proteins, often changing their activity or function.

Enzymes that remove phosphate groups from proteins, reversing the effects of kinases.

Proteins that bind to GTP and act as molecular switches in signaling pathways. They can be activated or inactivated by GTP binding and hydrolysis.

A large family of cell surface receptors involved in various cellular processes. These receptors bind to diverse signaling molecules, triggering intracellular signaling cascades. They are characterized by their seven transmembrane domains that traverse the cell membrane.

A type of signal transduction pathway that involves a series of proteins, including G proteins, adenylyl cyclase, and cAMP. It plays a crucial role in regulating cellular responses to a variety of stimuli, such as hormones, neurotransmitters, and light.

Heterotrimeric proteins composed of α, β, and γ subunits. They act as molecular switches, cycling between active and inactive states. They are involved in mediating the signal from GPCRs to downstream effectors.

A second messenger molecule that is produced by adenylyl cyclase. It plays a key role in regulating a diverse range of cellular processes, including glycogen metabolism, gene transcription, and muscle relaxation.

An enzyme that catalyzes the conversion of ATP to cAMP. Its activity is regulated by G protein signaling pathways.

A protein kinase that is activated by cAMP. It phosphorylates and regulates the activity of various target proteins, including glycogen phosphorylase kinase. This plays a critical role in metabolic processes and signal transduction.

A chemical molecule that serves as the signal that triggers the G protein signaling pathway. Examples include hormones like epinephrine and glucagon.

A process that amplifies the initial signal, leading to a larger and more robust cellular response. This is achieved by a series of cascading events involving multiple proteins.

A complex series of protein-protein interactions and modifications that relay a signal initiated by a ligand binding to a receptor. This often starts with GPCR activation and leads to downstream effects like changes in gene expression or metabolic processes.