Secreted protein that acts as a key regulator of lysosomal function and as a growth factor involved in inflammation, wound healing and cell proliferation (PubMed:12526812, PubMed:18378771, PubMed:28073925, PubMed:28453791, PubMed:28541286). Regulates protein trafficking to lysosomes, and also the activity of lysosomal enzymes (PubMed:28453791, PubMed:28541286). Also facilitates the acidification of lysosomes, causing degradation of mature CTSD by CTSB (PubMed:28073925). In addition, functions as a wound-related growth factor that acts directly on dermal fibroblasts and endothelial cells to promote division, migration and the formation of capillary-like tubule structures (By similarity). Also promotes epithelial cell proliferation by blocking TNF-mediated neutrophil activation preventing release of oxidants and proteases (PubMed:12526812). Moreover, modulates inflammation in neurons by preserving neurons survival, axonal outgrowth and neuronal integrity (PubMed:18378771). {ECO:0000250|UniProtKB:P28798, ECO:0000269|PubMed:12526812, ECO:0000269|PubMed:18378771, ECO:0000269|PubMed:28073925, ECO:0000269|PubMed:28453791, ECO:0000269|PubMed:28541286}. [Granulin-4]: Promotes proliferation of the epithelial cell line A431 in culture. [Granulin-3]: Inhibits epithelial cell proliferation and induces epithelial cells to secrete IL-8. . [Granulin-7]: Stabilizes CTSD through interaction with CTSD leading to maintain its aspartic-type peptidase activity. . This is the function of ENSG00000030582 (GRN, granulin precursor).