Telomerase and neurons: an unusual relationship.

Most people associate the enzyme telomerase with its role in maintaining telomeres, which is its best-known canonical role. For this important function, two main components are required: the protein telomerase reverse transcriptase (TERT) and the telomerase RNA component. In addition, over the last decades, an ever-growing number of other, non-telomeric, non-canonical functions for the telomerase protein TERT has been established. These reach from tumor promotion to decreasing oxidative stress and apoptosis as well as activating autophagy. These functions are more and more recognized as being important in many tissues and physiological as well as pathological conditions. The role of telomerase in brain development and neuronal cells has been investigated for more than 20 years. However, the non-telomeric role in non-dividing neurons of the brain for telomerase and the TERT-protein has only recently been highlighted by extensive research. Moreover, these developments promoted the suggestion of a beneficial and protective role of TERT against neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. This review summarizes the most important findings in the field of telomerase in neurons and gives an outlook onto possible therapeutic applications of boosting telomerase/TERT levels with telomerase activators to prevent or ameliorate various neurodegenerative diseases.