autocrine

Autocrine signaling is a form of cell communication in which a cell releases signaling molecules, or ligands, that bind to receptors on its own surface, thereby regulating its own activity. This contrasts with paracrine signaling (affecting neighboring cells), endocrine signaling (relying on circulatory transport to distant targets), and juxtacrine signaling (requiring direct cell-to-cell contact).

Mechanistically, a cell synthesizes a ligand and releases it into the extracellular environment. The ligand then binds to receptors on the same cell, triggering intracellular signaling cascades such as MAPK, JAK/STAT, or PI3K/AKT pathways. Autocrine signaling can reinforce cellular states, promote proliferation, survival, differentiation, or immune responses, and often involves feedback loops that modulate sensitivity to the signal.

Examples include immune cells producing interleukin-2 (IL-2) that acts on IL-2 receptors on the same cell to drive clonal expansion, and cancer cells that secrete growth factors like epidermal growth factor (EGF) that stimulate the same cells via the EGF receptor to support growth. Autocrine loops can also participate in development and tissue homeostasis, where cells regulate their own behavior in a local niche.

Clinical relevance: dysregulated autocrine signaling is implicated in diseases such as cancer, fibrosis, and autoimmune disorders. Therapeutic strategies sometimes aim to disrupt autocrine signaling, for example by targeting the ligand-receptor interaction or downstream pathways to limit cell proliferation or survival.