SMCT (sodium-coupled monocarboxylate transporter; slc5a8) is a Na+-coupled transporter for lactate, pyruvate and short-chain fatty acids. Similar to these already known substrates of SMCT, the water-soluble B-complex vitamin nicotinic acid also exists as a monocarboxylate anion (nicotinate) under physiological conditions. Therefore we evaluated the ability of SMCT to mediate the uptake of nicotinate. In mammalian cells, the cloned mouse SMCT (slc5a8) induced the uptake of nicotinate. The SMCT-induced uptake was Na+-dependent. The Michaelis constant for the uptake process was 296±88 μM. The Na+-activation kinetics indicated that at least two Na+ ions are involved in the process. Among the various structural analogues tested, nicotinate was the most effective substrate. Nicotinamide and methylnicotinate were not recognized by the transporter. 2-Pyrazine carboxylate and isonicotinate interacted with the transporter to a moderate extent. SMCT-mediated uptake of nicotinate was inhibited by lactate and pyruvate. In the Xenopus laevis oocyte expression system, SMCT-mediated nicotinate transport was electrogenic, as evident from the nicotinate-induced inward currents under voltage-clamp conditions. Substrate-induced currents in this expression system corroborated the substrate specificity determined in the mammalian cell expression system. The kinetic parameters with regard to the affinity of the transporter for nicotinate and the Hill coefficient for Na+ activation, determined by using the oocyte expression system, were also similar to those obtained from the mammalian cell expression system. We conclude that SMCT functions not only as a Na+-coupled transporter for short-chain fatty acids and lactate but also as a Na+-coupled transporter for the water-soluble vitamin nicotinic acid.
Skip Nav Destination
Article navigation
May 2005
-
Cover Image
Cover Image
- PDF Icon PDF LinkFront Matter
- PDF Icon PDF LinkTable of Contents
- PDF Icon PDF LinkEditorial Board
Research Article|
May 10 2005
Sodium-coupled and electrogenic transport of B-complex vitamin nicotinic acid by slc5a8, a member of the Na/glucose co-transporter gene family
Elangovan GOPAL;
Elangovan GOPAL
*Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912, U.S.A.
Search for other works by this author on:
You-Jun FEI;
You-Jun FEI
*Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912, U.S.A.
Search for other works by this author on:
Seiji MIYAUCHI;
Seiji MIYAUCHI
*Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912, U.S.A.
Search for other works by this author on:
Lina ZHUANG;
Lina ZHUANG
*Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912, U.S.A.
Search for other works by this author on:
Puttur D. PRASAD;
Puttur D. PRASAD
†Department of Obstetrics and Gynecology, Medical College of Georgia, Augusta, GA 30912, U.S.A.
Search for other works by this author on:
Vadivel GANAPATHY
Vadivel GANAPATHY
1
*Department of Biochemistry and Molecular Biology, Medical College of Georgia, Augusta, GA 30912, U.S.A.
†Department of Obstetrics and Gynecology, Medical College of Georgia, Augusta, GA 30912, U.S.A.
1To whom correspondence should be addressed (email vganapat@mail.mcg.edu).
Search for other works by this author on:
Publisher: Portland Press Ltd
Received:
November 17 2004
Revision Received:
January 03 2005
Accepted:
January 14 2005
Accepted Manuscript online:
January 14 2005
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London
2005
Biochem J (2005) 388 (1): 309–316.
Article history
Received:
November 17 2004
Revision Received:
January 03 2005
Accepted:
January 14 2005
Accepted Manuscript online:
January 14 2005
Citation
Elangovan GOPAL, You-Jun FEI, Seiji MIYAUCHI, Lina ZHUANG, Puttur D. PRASAD, Vadivel GANAPATHY; Sodium-coupled and electrogenic transport of B-complex vitamin nicotinic acid by slc5a8, a member of the Na/glucose co-transporter gene family. Biochem J 15 May 2005; 388 (1): 309–316. doi: https://doi.org/10.1042/BJ20041916
Download citation file:
Sign in
Don't already have an account? Register
Sign in to your personal account
You could not be signed in. Please check your email address / username and password and try again.
Captcha Validation Error. Please try again.