title: ZIP3, a new splice variant of the PKC-zeta-interacting protein family, binds to GABAC receptors, PKC-zeta, and Kv beta 2.
abstract: The correct targeting of modifying enzymes to ion channels and neurotransmitter receptors represents an important biological mechanism to control neuronal excitability. The recent cloning of protein kinase C-zeta interacting proteins (ZIP1, ZIP2) identified new scaffolds linking the atypical protein kinase PKC-zeta to target proteins. GABA(C) receptors are composed of three rho subunits (rho 1-3) that are highly expressed in the retina, where they are clustered at synaptic terminals of bipolar cells. A yeast two-hybrid screen for the GABA(C) receptor rho 3 subunit identified ZIP3, a new C-terminal splice variant of the ZIP protein family. ZIP3 was ubiquitously expressed in non-neuronal and neuronal tissues, including the retina. The rho 3-binding region of ZIP3 contained a ZZ-zinc finger domain, which interacted with 10 amino acids conserved in rho 1-3 but not in GABA(A) receptors. Consistently, only rho 1-3 subunits bound to ZIP3. ZIP3 formed dimers with ZIP1-3 and interacted with PKC-zeta and the shaker-type potassium channel subunit Kv beta 2. Different domains of ZIP3 interacted with PKC-zeta and the rho 3 subunit, and simultaneous assembly of ZIP3, PKC-zeta and rho 3 was demonstrated in vitro. Subcellular co-expression of ZIP3 binding partners in the retina supported the proposed protein interactions. Our results indicate the formation of a ternary postsynaptic complex containing PKC-zeta, ZIP3, and GABA(C) receptors.
authors.affiliation: Emil-Fischer-Zentrum, Institut für Biochemie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Fahrstrasse 17, 91054 Erlangen, Germany.
authors.forename: Cristina
authors.initials: C
authors.lastname: Croci
authors.forename: Johann Helmut
authors.initials: JH
authors.lastname: Brändstatter
authors.forename: Ralf
authors.initials: R
authors.lastname: Enz
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000378:metabolism; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D014644:Genetic Variation; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D006360:Heat-Shock Proteins; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D015221:Potassium Channels / Q000737:chemistry / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D011493:Protein Kinase C / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D018079:Receptors, GABA / Q000737:chemistry / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D000071456:Sequestosome-1 Protein; D000099221:Protein Kinase C zeta
chemical_list: D002352:Carrier Proteins; D005982:Glutathione Transferase; D006360:Heat-Shock Proteins; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D011493:Protein Kinase C; D018079:Receptors, GABA; D011993:Recombinant Fusion Proteins; D000071456:Sequestosome-1 Protein; D000099221:Protein Kinase C zeta; C087200:GABA-C receptor; C426239:Kcnab2 protein, rat; C491079:Sqstm1 protein, rat