Plays a role in protein ubiquitination, sorting and degradation through its association with VCP (By similarity). Involved in ubiquitin-mediated membrane proteins trafficking to late endosomes in an ESCRT-dependent manner, and hence plays a role in synaptic vesicle recycling (By similarity). May play a role in macroautophagy, regulating for instance the clearance of damaged lysosomes (By similarity). Plays a role in cerebellar Purkinje cell development. Positively regulates cytosolic and calcium-independent phospholipase A2 activities in a tumor necrosis factor alpha (TNF-alpha)- or lipopolysaccharide (LPS)-dependent manner, and hence prostaglandin E2 biosynthesis (By similarity). Interacts with ubiquitin. Interacts with UBXN6, VCP and YOD1; may form a complex involved in macroautophagy. Recruited to damaged lysosomes decorated with K48-linked ubiquitin chains. The PUL domain is composed of 6 armadillo-like repeats and mediates the interaction with VCP C-terminus. The PFU domain mediates interaction with ubiquitin. Belongs to the WD repeat PLAP family.