title: Novel functions of the phospholipase D2-Phox homology domain in protein kinase Czeta activation.
abstract: It has been established that protein kinase Czeta (PKCzeta) participates in diverse signaling pathways and cellular functions in a wide variety of cells, exhibiting properties relevant to cellular survival and proliferation. Currently, however, the regulation mechanism of PKCzeta remains elusive. Here, for the first time, we determine that phospholipase D2 (PLD2) enhances PKCzeta activity through direct interaction in a lipase activity-independent manner. This interaction of the PLD2-Phox homology (PX) domain with the PKCzeta-kinase domain also induces the activation loop phosphorylation of PKCzeta and downstream signal stimulation, as measured by p70 S6 kinase phosphorylation. Furthermore, only the PLD2-PX domain directly stimulates PKCzeta activity in vitro, and it is necessary for the formation of the ternary complex with phosphoinositide-dependent kinase 1 and PKCzeta. The mutant that substitutes the triple lysine residues (Lys101, Lys102, and Lys103) within the PLD2-PX domain with alanine abolishes interaction with the PKCzeta-kinase domain and activation of PKCzeta. Moreover, breast cancer cell viability is significantly affected by PLD2 silencing. Taken together, these results suggest that the PLD2-mediated PKCzeta activation is induced by its PX domain performing both direct activation of PKCzeta and assistance of activation loop phosphorylation. Furthermore, we find it is an important factor in the survival of breast cancer cells.
authors.affiliation: Division of Molecular and Life Sciences, Pohang University of Science and Technology, San 31, Hyojadong, Pohang 790-784, Republic of Korea.
authors.forename: Jong Hyun
authors.initials: JH
authors.lastname: Kim
authors.forename: Jung Hwan
authors.initials: JH
authors.lastname: Kim
authors.forename: Motoi
authors.initials: M
authors.lastname: Ohba
authors.forename: Pann-Ghill
authors.initials: PG
authors.lastname: Suh
authors.forename: Sung Ho
authors.initials: SH
authors.lastname: Ryu
mesh_terms: D064413:3-Phosphoinositide-Dependent Protein Kinases; D020816:Amino Acid Motifs; D000818:Animals; D001943:Breast Neoplasms / Q000201:enzymology* / Q000235:genetics; D019556:COS Cells; D002460:Cell Line; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D004789:Enzyme Activation; D020868:Gene Silencing; D006801:Humans; D047468:Immunoprecipitation; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D010739:Phospholipase D / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D010766:Phosphorylation; D025941:Protein Interaction Mapping; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D017434:Protein Structure, Tertiary; D034741:RNA, Small Interfering / Q000235:genetics / Q000494:pharmacology; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D000099221:Protein Kinase C zeta
chemical_list: D064413:3-Phosphoinositide-Dependent Protein Kinases; D007527:Isoenzymes; D010739:Phospholipase D; D011493:Protein Kinase C; D017346:Protein Serine-Threonine Kinases; D034741:RNA, Small Interfering; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D000099221:Protein Kinase C zeta; C105606:phospholipase D2