Transthyretin: a multifaceted protein.

Transthyretin is a highly conserved homotetrameric protein, mainly synthetized by the liver and the choroid plexus of brain. The carrier role of TTR is well-known; however, many other functions have emerged, namely in the nervous system. Behavior, cognition, neuropeptide amidation, neurogenesis, nerve regeneration, axonal growth and 14-3-3ζ metabolism are some of the processes where TTR has an important role. TTR aggregates are responsible for many amyloidosis such as familial amyloidotic polyneuropathy and cardiomyopathy. Normal TTR can also aggregate and deposit in the heart of old people and in preeclampsia placental tissue. Differences in TTR levels have been found in several neuropathologies, but its neuroprotective role, until now, was described in ischemia and Alzheimer's disease. The aim of this review is to stress the relevance of TTR, besides its well-known role on transport of thyroxine and retinol-binding protein.