title: Deoxyhypusine synthase is phosphorylated by protein kinase C in vivo as well as in vitro.
abstract: Deoxyhypusine synthase catalyzes the first step in the posttranslational synthesis of an unusual amino acid, hypusine, in the eukaryotic translation initiation factor 5A (eIF-5A) precursor protein. We earlier observed that yeast recombinant deoxyhypusine synthase was phosphorylated by protein kinase C (PKC) in vitro (Kang and Chung, 1999) and the phosphorylation rate was synergistically increased to a 3.5-fold following treatment with phosphatidylserine (P.Ser)/diacylglycerol (DAG)/ Ca(2+), suggesting a possible involvement of PKC. We have extended study on the phosphorylation of deoxyhypusine synthase in vivo in different cell lines in order to define its role on the regulation of eIF5A in the cell. Deoxyhypusine synthase was found to be phosphorylated by endogenous kinases in CHO, NIH3T3, and chicken embryonic cells. The highest degree of phosphorylation was found in CHO cells. Moreover, phosphorylation of deoxyhypusine synthase in intact CHO cells was revealed and the expression of phosphorylated deoxyhypusine synthase was significantly diminished by diacyl ethylene glycol (DAEG), a PKC inhibitor, and enhanced by phorbol 12-myristate 13-acetate (PMA) or Ca(2+)/DAG. Endogenous PKC in CHO cell and cell lysate was able to phosphorylate deoxyhypusine synthase and this modification is enhanced by PMA or Ca(2+) plus DAG. Close association of PKC with deoxyhypusine synthase in the CHO cells was evident in the immune coprecipitation and was PMA-, and Ca(2+)/phospholipid dependent. These results suggest that phosphorylation of deoxyhypusine synthase was PKC-dependent cellular event and open a path for possible regulation in the interaction with eIF5A precursor for hypusine synthesis.
authors.affiliation: Department of Biochemistry, Gyeongsang National University College of Medicine, Chinju 660-751, South Korea. krkang@gaechuk.gsnu.ac.kr
authors.forename: Kee Ryeon
authors.initials: KR
authors.lastname: Kang
authors.forename: Jee-Sook
authors.initials: JS
authors.lastname: Kim
authors.forename: Soo Il
authors.initials: SI
authors.lastname: Chung
authors.forename: Myung Hee
authors.initials: MH
authors.lastname: Park
authors.forename: Yeon Woong
authors.initials: YW
authors.lastname: Kim
authors.forename: Dongkwon
authors.initials: D
authors.lastname: Lim
authors.forename: So-Young
authors.initials: SY
authors.lastname: Lee
mesh_terms: D000818:Animals; D002460:Cell Line; D002642:Chick Embryo; D006224:Cricetinae; D005260:Female; D051379:Mice; D000587:Oxidoreductases Acting on CH-NH Group Donors / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D000587:Oxidoreductases Acting on CH-NH Group Donors; C063507:deoxyhypusine synthase; D011493:Protein Kinase C