Ap3d1, encoding the AP-3δ subunit of the adaptor-related protein complex 3 (AP-3), is crucial for the biogenesis, function, and trafficking of secretory lysosomes [5,7]. The AP-3 complex is involved in sorting proteins to lysosomes and lysosome-related organelles [8]. Genetic studies on Ap3d1 can provide insights into its functions in normal biological processes and disease mechanisms.

In zebrafish, Ap3d1 knockout recapitulates the crasher mutant phenotype, with significant expression changes in melanogenesis genes dct and tyrp1b, and it promotes melanophore survival by limiting excessive autophagy [2]. In mice, loss of optineurin leads to AP3D1-mediated lysosomal sorting and degradation of palmitoylated IFNGR1, driving cancer immune evasion and immunotherapy resistance in colorectal cancer [1]. Mutations in human AP3D1 are associated with Hermansky-Pudlak syndrome type 10 (HPS10), characterized by oculocutaneous albinism, immunodeficiency, neurodevelopmental delay, hearing loss, and neurological abnormalities [4,5,7]. Serum anti-AP3D1 antibodies are risk factors for acute ischemic stroke related to atherosclerosis [3]. Also, in a mouse model of acute gouty arthritis, lncRNA SNHG8 accelerates the disease development by upregulating AP3D1 in an miR-542-3p-dependent way [6].

In conclusion, Ap3d1 is essential for lysosome-related processes. Gene-knockout models in zebrafish and mice, along with human genetic studies, have revealed its role in melanogenesis, cancer immune evasion, HPS10-related disorders, atherosclerosis-related stroke, and acute gouty arthritis. Understanding Ap3d1 functions can potentially lead to new therapeutic strategies for these associated diseases.