PPT1 and infantile neuronal ceroid lipofuscinosis: The pre-synaptic chaperone cysteine string protein α (CSPα, DNAJ5), which is mutated in adult-onset neuronal ceroid lipofuscinosis (CLN4), is a PPT1 substrate in a cell-free preparation (Nosková et al., 2011; Henderson et al., 2016; Figure 2B).