IRIP, a new ischemia/reperfusion-inducible protein that participates in the regulation of transporter activity.
We report the identification and characterization of a new ischemia/reperfusion-inducible protein (IRIP), which belongs to the SUA5/YrdC/YciO protein family. IRIP cDNA was isolated in a differential display analysis of an ischemia/reperfusion-treated kidney RNA sample. Mouse IRIP mRNA was expressed in all tissues tested, the highest level being in the testis, secretory, and endocrine organs. Besides ischemia/reperfusion, endotoxemia also activated the expression of IRIP in the liver, lung, and spleen. The transporter regulator RS1 was identified as an IRIP-interacting protein in yeast two-hybrid screening. The interaction between IRIP and RS1 was further confirmed in coimmunoprecipitation assays. A possible role of IRIP in regulating transporter activity was subsequently investigated. IRIP overexpression inhibited endogenous 1-methyl-4-phenylpyridinium (MPP+) uptake activity in HeLa cells. The activities of exogenous organic cation transporters (OCT2 and OCT3), organic anion transporter (OAT1), and monoamine transporters were also inhibited by IRIP. Conversely, inhibition of IRIP expression by small interfering RNA or antisense RNA increased MPP+ uptake. We measured transport kinetics of OCT2-mediated uptake and demonstrated that IRIP overexpression significantly decreased V(max) but did not affect K(m). On the basis of these results, we propose that IRIP regulates the activity of a variety of transporters under normal and pathological conditions.
Jiang
Wei
W
Department of Biochemistry, Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08854, USA.
Prokopenko
Olga
O
Wong
Lawrence
L
Inouye
Masayori
M
Mirochnitchenko
Oleg
O
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology; D006367:HeLa Cells; D006801:Humans; D026901:Membrane Transport Proteins / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000378:metabolism; D015427:Reperfusion Injury / Q000378:metabolism*; D013997:Time Factors; D014158:Transcription, Genetic; D020798:Two-Hybrid System Techniques
D002352:Carrier Proteins; C503577:IRIP protein, mouse; D026901:Membrane Transport Proteins; D012333:RNA, Messenger