Secreted protein that acts as a key regulator of lysosomal function and as a growth factor involved in inflammation, wound healing and cell proliferation (  ). Regulates protein trafficking to lysosomes and, also the activity of lysosomal enzymes (, ). Facilitates also the acidification of lysosomes, causing degradation of mature CTSD by CTSB . 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 . Moreover, modulates inflammation in neurons by preserving neurons survival, axonal outgrowth and neuronal integrity .
Promotes proliferation of the epithelial cell line A431 in culture.
Inhibits epithelial cell proliferation and induces epithelial cells to secrete IL-8.
Stabilizes CTSD through interaction with CTSD leading to maintain its aspartic-type peptidase activity.
Subcellular locations: Secreted, Lysosome
Endocytosed by SORT1 and delivred to lysosomes (, ). Targeted to lysosome by PSAP via M6PR and LRP1, in both biosynthetic and endocytic pathways (, ). Co-localized with GBA1 in the intracellular trafficking compartments until to lysosome (By similarity).
In myelogenous leukemic cell lines of promonocytic, promyelocytic, and proerythroid lineage, in fibroblasts, and very strongly in epithelial cell lines. Present in inflammatory cells and bone marrow. Highest levels in kidney.