In conclusion, both OPTN and its upstream protein TBK1 are required for normal mitophagy homeostasis.178 As shown in these studies, TBK1 phosphorylates OPTN, enhancing its ability to bind to ubiquitinated mitochondria, suggesting that TBK1 may also be one of the potential targets for treating ALS.94 Here, TBK1 is linked to amyotrophic lateral sclerosis.