Identification of the multivalent PDZ protein PDZK1 as a binding partner of sodium–coupled monocarboxylate transporter SMCT1 (SLC5A8) and SMCT2 (SLC5A12)
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Sodium-coupled monocarboxylate transporters SMCT1 (SLC5A8) and SMCT2 (SLC5A12) mediate the high- and low-affinity transport of lactate in the kidney, but their regulatory mechanism is still unknown. Since these two transporters have the PDZ-motif at their C-terminus, the function of SMCTs may be modulated by a protein–protein interaction. To investigate the binding partner(s) of SMCTs in the kidney, we performed yeast two-hybrid (Y2H) screenings of a human kidney cDNA library with the C-terminus of SMCT1 (SMCT1-CT) and SMCT2 (SMCT2-CT) as bait. PDZK1 was identified as a partner for SMCTs. PDZK1 coexpression in SMCT1-expressing HEK293 cells enhanced their nicotinate transport activity. PDZK1, SMCT1, and URAT1 in vitro assembled into a single tri-molecular complex and their colocalization was confirmed in the renal proximal tubule in vivo by immunohistochemistry. These results indicate that the SMCT1-PDZK1 interaction thus plays an important role in both lactate handling as well as urate reabsorption in the human kidney.
KeywordsMonocarboxylates Monocarboxylate transporter SMCT Lactate PDZ PDZK1
Urate transporter 1
Sodium–coupled monocarboxylate transporter
PSD-95, DglA, and ZO-1
The authors thank A. Toki, R. Kofuji, A. Yamanishi, and H. Miyazaki for technical assistance. This work was supported in part by Grants from JSPS (KAKENHI 15590233, 18590900, 21390073, 26461258, 18K08200), the Salt Science Research Foundation (No. 0524, 0721), The Nakatomi Foundation, Gout Research Foundation of Japan, and Kyorin University School of Medicine (Collaborative Project 2009) to N.A. This work was presented in part at the Renal Week 2006 of the American Society of Nephrology, San Diego, CA, November 2006, and at the Annual Meeting of Experimental Biology 2008, San Diego, CA, April 2008.
NA designed the study. SS and NA performed the Y2H. NA, KN and SM checked and confirmed the experimental materials and data used in this study. SS and XH performed the transport assay. SS, TK and TF performed the biochemical and immunohistochemical analysis. SS, NA and HS wrote the manuscript. All authors discussed the results and commented on the manuscript.
Compliance with ethical standards
Conflict of interest
All authors of this manuscript declare that we have no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
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