Recruitment of protein kinase D to the trans-Golgi network via the first cysteine-rich domain

Protein kinase D (PKD) is a cytosolic protein, which upon binding to the tr ans-Golgi network (TGN) regulates the fission of transport carriers specifi cally destined to the cell surface. We have found that the first cysteine-r ich domain (C1a), but not the second cysteine-rich domain (C1b), is suffici ent for the binding of PKD to the TGN. Proline 155 in C1a is necessary for the recruitment of intact PKD to the TGN. Whereas C1a is sufficient to targ et a reporter protein to the TGN, mutation of serines 744/748 to alanines i n the activation loop of intact PKD inhibits its localization to the TGN. M oreover, anti-phospho-PKD antibody, which recognizes only the activated for m of PKD, recognizes the TGN-bound PKD. Thus, activation of intact PKD is i mportant for binding to the TGN.