Abstract

Sedlin is implicated in a diverse set of cellular roles that include membrane trafficking and gene regulation. Mutations in sedlin lead to a skeletal disorder called SEDT. However, a complete understanding of the function(s) of sedlin remains elusive. Sedlin is one component of a large heteromeric complex called TRAPP ( tra nsport p rotein p article) that is involved in membrane traffic between the endoplasmic reticulum and the Golgi. To begin to characterize the function of sedlin a yeast two-hybrid (Y2H) screen was performed. This screen identified a novel sedlin interactor called SPATA4. The interaction was confirmed both in vitro , using an MBP-pulldown assay, and in vivo , using coimmunoprecipitation. A gel filtration experiment showed that SPATA4 co-fractionates with the TRAPP complex, a result that was supported by in vitro work. Since SPATA4 was originally identified as a protein involved in spermatogenesis, the interaction between TRAPP and SPATA4 may suggest a specialized role for TRAPP and/or TRAPP isocomplexes in spermatogenesis. Alternatively, SPATA4 may play a previously unreported role in membrane traffic. A bioinformatic analysis of SPATA4 revealed a domain found in another potential sedlin-interactor called SPEF1. A portion of this domain is known to mediate interaction with microtubules. Taken together, the SPATA4- TRAPP interaction may link the TRAPP vesicle tethering complex to the cytoskeleton which transports Golgi-destined vesicles