Inhibition of beta 1 syntrophin decreased ABCA 1 protein levels , whereas overexpression of beta 1 syntrophin increased ABCA 1 cell surface expression and stimulated efflux to apolipoprotein A 1 . ^^^ These findings indicate that beta 1 syntrophin acts through a class 1 PDZ interaction with the C terminus of ABCA 1 to regulate the cellular distribution and activity of the transporter . ^^^ The approach used to identify beta 1 syntrophin as an ABCA 1 binding protein should prove useful in elucidating other protein interactions upon which ABCA 1 function depends . . ^^^ |