Plays a role in protein ubiquitination, sorting and degradation through its association with VCP. Involved in ubiquitin-mediated membrane proteins trafficking to late endosomes in an ESCRT-dependent manner, and hence plays a role in synaptic vesicle recycling. May play a role in macroautophagy, regulating for instance the clearance of damaged lysosomes. 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. 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.