===== CD63 =====

**CD63** is a transmembrane protein of the tetraspanin family commonly found in the membrane of [[extracellular_vesicle|extracellular vesicles]], particularly exosomes. It is widely used as a **biomarker for EV identification and isolation**.

==== Structure and Function ====
  * Four transmembrane domains
  * Localized in late endosomes, lysosomes, and exosomes
  * Involved in:
    * Vesicle formation and trafficking
    * Protein sorting
    * Cell adhesion and immune modulation

==== In EV Engineering ====
CD63 is often used as a **molecular scaffold** for displaying functional tags or facilitating **selective cargo loading** in synthetic or engineered EVs, such as in the [[engineering_cd63_evs|E-NoMi system]].