Specific isoforms of actin-binding proteins on distinct populations of Golgi-derived vesicles

Golgi membranes and Golgi-derived vesicles are associated with multiple cyt oskeletal proteins and motors, the diversity and distribution of which have not yet been defined. Carrier vesicles were separated from Golgi membranes , using an in vitro budding assay, and different populations of vesicles we re separated using sucrose density gradients. Three main populations of ves icles labeled with beta-COP, gamma-adaptin, or p200/myosin II were separate d and analyzed for the presence of actin/actin-binding proteins, beta-Actin was bound to Golgi cisternae and to all populations of newly budded vesicl es. Centractin was selectively associated with vesicles co-distributing wit h beta-COP-vesicles, while p200/myosin II (non-muscle myosin IIA) and non-m uscle myosin IIB were found on different vesicle populations. Isoforms of t he Tm5 tropomyosins were found on selected Golgi-derived vesicles, while ot her Tm isoforms did not colocalize with Tm5 indicating the association of s pecialized actin filaments with Golgi-derived vesicles. Golgi-derived vesic les were shown to bind to F-actin polymerized from cytosol with Jasplakinol ide. Thus, newly budded, coated vesicles derived from Golgi membranes can b ind to actin and are customized for differential interactions with microfil aments by the presence of selective arrays of actin-binding proteins.