Interaction of the retinoblastoma gene product, RB, with cyclophilin A negatively affects cyclosporin-inhibited NFAT signaling.
The retinoblastoma susceptibility gene product, p105Rb (RB), is generally believed to be an important regulator in the control of cell growth, differentiation, and apoptosis. Several cellular factors that form complexes with RB and exert their cellular regulatory functions have been identified, such as the newly identified RB:cyclophilin A (CypA) complex. The physical interactions between RB and CypA were demonstrated by glutathione S-transferase affinity matrix binding assays and immunoprecipitation, followed by Western blot analyses. The N-terminal region of CypA mediated the interaction with RB, whereas the region upstream of the A-pocket of RB was required for binding to CypA. Ectopic expression of RB into Jurkat cells partially blocks the function of cyclosporin (CsA) to inhibit nuclear factor for activation of T cell (NFAT) activation by phorbol ester (PMA) plus ionomycin A (IA), suggesting that RB may prevent CsA inhibition of T lymphocyte activation. These results are further evidenced by the effect of RB on both calcineurin (CN) and NFAT binding activity in vitro, suggesting that the interaction of RB with CypA interferes with the CsA:CypA complex and blocks CsA-inhibited CN activity. These data reveal the functional link between RB and CypA and their involvement in T cell activation signaling.
Cui
Yukun
Y
Dental Research Institute, UCLA School of Dentistry, Los Angeles, California 90095, USA.
Mirkia
Kirash
K
Florence Fu
Yu-Hsieh
YH
Zhu
Li
L
Yokoyama
Kazunari K
KK
Chiu
Robert
R
D015153:Blotting, Western; D019703:Calcineurin / Q000378:metabolism; D065095:Calcineurin Inhibitors; D021984:Cyclophilin A / Q000378:metabolism* / Q000494:pharmacology; D016572:Cyclosporine / Q000378:metabolism / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000502:physiology; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D015759:Ionomycin / Q000737:chemistry / Q000494:pharmacology; D019169:Jurkat Cells / Q000378:metabolism; D008213:Lymphocyte Activation / Q000187:drug effects / Q000502:physiology*; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D010703:Phorbol Esters / Q000494:pharmacology; D010957:Plasmids; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism*; D017384:Sequence Deletion; D013379:Substrate Specificity; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D014157:Transcription Factors / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000494:pharmacology* / Q000502:physiology
D065095:Calcineurin Inhibitors; D004268:DNA-Binding Proteins; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D010703:Phorbol Esters; D011993:Recombinant Fusion Proteins; D016160:Retinoblastoma Protein; D014157:Transcription Factors; D015759:Ionomycin; D016572:Cyclosporine; D005982:Glutathione Transferase; D019703:Calcineurin; D021984:Cyclophilin A