DCC-interacting protein 13-alpha

APPL1 (DCC-interacting protein 13-alpha) is a multifunctional adapter protein that regulates cell proliferation, immune response, endosomal trafficking, and metabolic processes through interactions with membrane receptors, signaling proteins, and nuclear factors (UniProt: Q9UKG1). It modulates RAB5A-dependent signaling, controls TLR4 and PI3K/Akt pathways in immune cells, and regulates TGFBR1 nuclear trafficking. The protein also plays roles in adiponectin and insulin signaling, fibroblast migration, and Wnt/beta-catenin transcription.

APPL1 is associated with maturity-onset diabetes of the young 14 (MODY14), an autosomal dominant form of early-onset diabetes marked by defective insulin secretion (UniProt: Q9UKG1, MIM 616511). The protein's involvement in insulin and adiponectin signaling pathways reflects its broader role in metabolic regulation.

In Alzheimer's disease, APPL1 shows an ambiguous direction of regulation across subcellular fractions in post-mortem AD brain compared to age-matched controls (Chaparral AD proteomics). The mean log2 fold-change is −0.0841, indicating minimal net change, though this masks potential redistribution across the two measured fractions.