GORASP2 (GRASP55) localizes to the median region of Golgi, where it forms a complex with BLZF1 (Golgin 45) and RAB2A GTPase (Short et al. 2001). Similar to GORASP1, GORASP2 is involved in the maintenance of Golgi structure and positively regulates stacking of Golgi cisternae (Xiang and Wang 2010). In addition, GORASP2, probably through its association with RAB2A GTPase, regulates trafficking through the Golgi (Short et al. 2001). In G2 and mitotic prophase, GORASP2 is phosphorylated by MEK1/2 activated MAP kinases. Monophosphorylated MAPK3 (ERK1) isoform, MAPK3 3 i.e. ERK1b (known as ERK1c in rat), likely activated by a MEK1 isoform MEK1b (Shaul et al. 2009), as well as MAPK1 (ERK2) are implicated in GORASP2 phosphorylation during mitosis (Jesch et al. 2001, Colanzi et al. 2003, Shaul and Seger 2006, Feinstein and Linstedt 2007, Duran et al. 2008, Feinstein and Linstedt 2008). Threonine residues T222 and T225 were implicated as targets of MAPK mediated GORASP2 phosphorylation in studies that used directional mutagenesis (Jesch et al. 2001, Feinstein and Linstedt 2008). However both T222 and T225 were simultaneously mutated in these studies and their roles have not been individually investigated. Using mass spectroscopy, T225 but not T222 was identified as a GORASP2 residue phosphorylated by mitotic cytosol (Duran et al. 2008). T249 residue of GORASP2 was also phosphorylated by mitotic cytosol, but the involvement of ERKs in T249 phosphorylation has not been examined (Duran et al. 2008).