In neurons, involved in the transport of late endosomes/lysosomes (PubMed:25066864). May be involved in dendrite morphogenesis and maintenance by regulating lysosomal trafficking (PubMed:25066864). May act as a molecular brake for retrograde transport of late endosomes/lysosomes, possibly via its interaction with MAP6 (By similarity). In motoneurons, may mediate the axonal transport of lysosomes and axonal sorting at the initial segment (By similarity). It remains unclear whether TMEM106B affects the transport of moving lysosomes in the anterograde or retrograde direction in neurites and whether it is important in the sorting of lysosomes in axons or in dendrites (By similarity). In neurons, may also play a role in the regulation of lysosomal size and responsiveness to stress (PubMed:25066864). Required for proper lysosomal acidification (By similarity). {ECO:0000250|UniProtKB:Q6AYA5, ECO:0000250|UniProtKB:Q80X71, ECO:0000269|PubMed:25066864}. (Microbial infection) Plays a role in human coronavirus SARS- CoV-2 infection, but not in common cold coronaviruses HCoV-229E and HCoV-OC43 infections. Involved in ACE2-independent SARS-CoV-2 cell entry. Required for post-endocytic stage of virus entry, facilitates spike-mediated membrane fusion. Virus attachment and endocytosis can also be mediated by other cell surface receptors. {ECO:0000269|PubMed:33333024, ECO:0000269|PubMed:33686287, ECO:0000269|PubMed:37421949}. This is the function of TMEM106B (transmembrane protein 106B, Ensembl gene identifier ENSG00000106460).