Inhibition of the c-Jun N-terminal kinase/AP-1 and NF-kappaB pathways by PICOT, a novel protein kinase C-interacting protein with a thioredoxin homology domain.
Protein kinase C-theta (PKCtheta) is a Ca(2+)-independent PKC isoform that is selectively expressed in T lymphocytes (and muscle), and is thought to play an important role in T cell receptor-induced activation. To gain a better understanding of the function and regulation of PKCtheta, we have employed the yeast two-hybrid system to identify PKCtheta-interacting proteins. We report the isolation and characterization of a cDNA encoding a novel 335-amino acid (37. 5-kDa) PKCtheta-interacting protein termed PICOT (for PKC-interacting cousin of thioredoxin). PICOT is expressed in various tissues, including in T cells, where it colocalizes with PKCtheta. PICOT displays an N-terminal thioredoxin homology domain, which is required for the interaction with PKC. Comparison of the unique C-terminal region of PICOT with expressed sequence tag data bases revealed two tandem repeats of a novel domain that is highly conserved from plants to mammals. Transient overexpression of full-length PICOT (but not its N- or C-terminal fragments) in T cells inhibited the activation of c-Jun N-terminal kinase (but not extracellular signal-regulated kinase), and the transcription factors AP-1 or NF-kappaB. These findings suggest that PICOT and its evolutionary conserved homologues may interact with PKC-related kinases in multiple organisms and, second, that it plays a role in regulating the function of the thioredoxin system.
Witte
S
S
Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121, USA.
Villalba
M
M
Bi
K
K
Liu
Y
Y
Isakov
N
N
Altman
A
A
D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000737:chemistry* / Q000494:pharmacology / Q000502:physiology*; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D019169:Jurkat Cells; D008213:Lymphocyte Activation / Q000502:physiology; D020935:MAP Kinase Signaling System / Q000187:drug effects; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors*; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000037:antagonists & inhibitors*; D010957:Plasmids; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D013601:T-Lymphocytes / Q000187:drug effects; D013879:Thioredoxins / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000037:antagonists & inhibitors*; D014162:Transfection; D020798:Two-Hybrid System Techniques
D002352:Carrier Proteins; C404105:GLRX3 protein, human; D016328:NF-kappa B; D011993:Recombinant Fusion Proteins; D018808:Transcription Factor AP-1; D013879:Thioredoxins; D005982:Glutathione Transferase; D011493:Protein Kinase C; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases