TMP21, a type I transmembrane protein, is a member of the p24 cargo protein family, which is highly enriched in the ER, the Golgi and coat protein (COP) I and II transport vesicles (1,2). TMP21 is involved in protein transport and vesicular targeting. In particular, TMP21 influences APP trafficking by stabilizing nascent APP. The absence of TMP21 leads to enhanced maturation and cell surface accumulation of APP (3). In addition, TMP21 is a non-essential component of the γ-secretase complex with the potential to modulate γ-secretase mediated cleavage and Aβ production without having an effect on ε-secretase activity (4). |