Syndecan-4

Syndecan-4 (SDC4) is a cell surface proteoglycan that regulates exosome biogenesis through coordinated interactions with SDCBP and PDCD6IP (UniProt: P31431). At 21.6 kDa, this transmembrane protein plays a role in extracellular vesicle biogenesis, a process relevant to cellular communication and protein trafficking.

SDC4 is expressed across tissues and participates in broader syndecans-mediated signaling pathways (UniProt: P31431). While no primary disease associations are documented in UniProt, the protein's involvement in exosome regulation connects it to cellular homeostasis mechanisms.

In Alzheimer's disease, syndecan-4 is significantly upregulated in post-mortem AD brain tissue relative to age-matched controls (Chaparral AD proteomics). Quantitative proteomic analysis across four subcellular fractions (P2, P3, S2, S3) detected a mean log2 fold-change of +0.55, indicating modest but consistent elevation. This upregulation may reflect altered exosome biogenesis or extracellular vesicle dynamics in the AD brain, potentially influencing amyloid or tau pathology propagation.