UBQLN2 and frontotemporal dementia: Consistent with the present findings in HEK-293T cells, a recent study reported no dysfunction of the proteasome examined by the Suc-AMC substrate in Hela cells that overexpressed ALS/FTD-linked UBQLN2 mutants (P497H, P497S, P506T, P509S, or P525S) [16].