Mechanisms of action of angiogenin.

Angiogenin induces angiogenesis by activating vessel endothelial and smooth muscle cells and triggering a number of biological processes, including cell migration, invasion, proliferation, and formation of tubular structures. It has been reported that angiogenin plays its functions mainly through four pathways: (1) exerting its ribonucleolytic activity; (2) binding to membrane actin and then inducing basement membrane degradation; (3) binding to a putative 170-kDa protein and subsequently transducing signal into cytoplasm; and (4) translocating into the nucleus of target cells directly and then enhancing ribosomal RNA transcription. Angiogenin can also translocate into the nucleus of cancer cells and induces the corresponding cell proliferation. Furthermore, angiogenin has neuroprotective activities in the central nervous system and the loss of its function may be related to amyotrophic lateral sclerosis. This review intends to conclude the mechanisms underlying these actions of angiogenin and give a perspective on future research.