Chemoattractant

A chemoattractant is a chemical substance that induces chemotaxis, the directed movement of cells toward higher concentrations of the substance. Chemoattractants create gradients that are detected by cell surface receptors, guiding migration in processes such as immune responses, development, and wound healing.

Mechanism works by receptor engagement that activates intracellular signaling pathways. In animals, this often involves G protein-coupled receptors; in bacteria, two-component sensor systems contribute. Signaling cascades lead to polarized cytoskeletal rearrangements and directional movement toward the source of the attractant.

Sources and classes of chemoattractants include a variety of molecules. In humans, cytokines and chemokines (such as IL-8/CXCL8 and C5a) attract leukocytes; lipid mediators like leukotrienes and prostaglandins also function as attractants; small peptides such as N-formylated methionyl peptides (fMLP) attract neutrophils. Bacteria release attractants such as formylated peptides and metabolic byproducts that guide swarming and colonization.

Receptors involved include chemokine receptors (a subset of GPCRs) such as CXCR1/2, formyl peptide receptors, and other GPCRs. In bacteria, signal detection often relies on two-component systems. Receptor activation translates into intracellular signals that modulate actin dynamics, directionality, and speed of migration.

Physiological and clinical relevance includes rapid leukocyte recruitment to infection and sites of tissue injury, as well as roles in development and wound healing. Dysregulated chemotaxis can contribute chronic inflammation, autoimmune disorders, and cancer metastasis. Therapeutic approaches aim to modulate chemotaxis by targeting chemoattractants, their receptors, or downstream signaling pathways.