Related Experiment Video

Updated: Aug 16, 2026

Characterization of Membrane Transporters by Heterologous Expression in E. coli and Production of Membrane Vesicles
13:16

Characterization of Membrane Transporters by Heterologous Expression in E. coli and Production of Membrane Vesicles

Published on: December 31, 2019

Molecular and functional characterization of organic cation/carnitine transporter family in mice

I Tamai1, R Ohashi, J I Nezu

  • 1Faculty of Pharmaceutical Sciences, Kanazawa University, Kanazawa 920-0934, Japan.

The Journal of Biological Chemistry
|September 30, 2000
PubMed

Insights

Researchers identified new organic cation transporters, OCTN1 and OCTN3, in mice. OCTN3 shows high specificity for carnitine transport, while OCTN1 primarily transports tetraethylammonium, suggesting distinct roles in carnitine deficiency disorders.

Area of Science:

  • Molecular Biology
  • Genetics
  • Biochemistry

Background:

  • Carnitine is crucial for fatty acid beta-oxidation.
  • Defects in carnitine transport cause systemic carnitine deficiency.
  • The organic cation/carnitine transporter OCTN2 is a known cause of this deficiency.

Purpose of the Study:

  • To isolate and characterize novel organic cation/carnitine transporter family members, OCTN1 and OCTN3, in mice.
  • To elucidate the substrate specificity and transport mechanisms of OCTN1, OCTN2, and OCTN3.
  • To understand the potential roles of these transporters in carnitine metabolism and deficiency.

Main Methods:

  • Isolation and characterization of mouse OCTN1 and OCTN3 cDNAs.
  • Transfection of HEK293 cells with OCTN cDNAs to assess transport activity.
  • Measurement of carnitine and tetraethylammonium (TEA) uptake in transfected cells.
  • Analysis of Na(+) dependence for carnitine transport by each OCTN member.

Main Results:

  • OCTN1, OCTN2, and OCTN3 are expressed in the kidney; OCTN1 and OCTN2 in various tissues; OCTN3 predominantly in the testis.
  • OCTN1 and OCTN2 exhibit Na(+)-dependent carnitine transport, while OCTN3 shows Na(+)-independent transport.
  • OCTN1 and OCTN2 transport TEA, but OCTN3 does not.
  • OCTN3 demonstrates high specificity for carnitine (uptake ratio 746:1), whereas OCTN1 shows minimal carnitine transport (1.78:1) and significant TEA transport.

Conclusions:

  • OCTN3 is unique due to its limited tissue distribution and Na(+)-independent carnitine transport.
  • OCTN1 exhibits distinct functional properties, primarily transporting TEA with minimal carnitine transport, suggesting a different physiological role.
  • These findings expand our understanding of the carnitine transporter family and their implications in metabolic disorders.

More Related Videos

Selection of Transporter-Targeted Inhibitory Nanobodies by Solid-Supported-Membrane (SSM)-Based Electrophysiology09:12

Selection of Transporter-Targeted Inhibitory Nanobodies by Solid-Supported-Membrane (SSM)-Based Electrophysiology

Published on: May 3, 2021

Characterizing Mammalian Zinc Transporters Using an In Vitro Zinc Transport Assay07:55

Characterizing Mammalian Zinc Transporters Using an In Vitro Zinc Transport Assay

Published on: June 2, 2023

Related Concept Videos

The Significance of Membrane Transport01:44

The Significance of Membrane Transport

The transport of solutes across the cell membrane is essential for metabolic processes, like maintaining cell size and volume, generating the action potential, exchanging nutrients and gases, etc. Membrane transport can be either passive or active. It can be simple diffusion, facilitated, or mediated transport aided by transport proteins such as transporters and channels.
Transporters facilitate either an active or passive movement of solutes. They can allow a single-molecule transport down its...
Membrane Transporters01:31

Membrane Transporters

Transporters are essential membrane transport proteins with functions related to cell nutrition, homeostasis, communication, etc. Approximately 7% of all genes in the human genome code for transporters or transporter-related proteins.
Transporters are mainly composed of alpha-helices, built from bundles of ten or more helices traversing the plasma membrane. The solute-binding sites are located midway, where some of the helices are broken or distorted, making space for the binding site through...
ABC Transporters: Exporter01:31

ABC Transporters: Exporter

ATP-binding cassette or ABC transporter is the largest superfamily of integral membrane proteins. The transporters have transmembrane-binding domains (TMDs) and nucleotide-binding domains (NBDs). The TMDs are specific to their substrates, whereas the NBDs are similar to engines that complete ATP hydrolysis to complete the substrate transport. They can be full transporters consisting of two TMDs and NBDs, half transporters with one TMD and NBD, while some encoded with a single TMD or NBD are...
ABC Transporters: Importer01:27

ABC Transporters: Importer

ATP-binding cassette or ABC transporters are a class of ATP-driven pumps that hydrolyze ATP to move solutes across the membrane. They can be grouped into importers and exporters. While exporters are present in all domains of life, importers exist only in bacteria and some plants.
In bacteria, based on the number of transmembrane helices and the chemical nature of their substrates, the ABC importers can be divided into three types:
Carrier-Mediated Transport01:06

Carrier-Mediated Transport

Carrier-mediated transport is a pivotal process in drug absorption, particularly for lipid-insoluble drugs, and encompasses facilitated diffusion and active transport. Facilitated diffusion allows drugs to move along their concentration gradient without energy expenditure, while active transport utilizes ATP to drive drug movement against this gradient.
Active transport involves two types of membrane-spanning transporters: uptake and efflux. Uptake transporters are expressed in the small...
Pharmacogenetics of Drug Transporters: P-Glycoprotein and Solute Carrier Transporters01:16

Pharmacogenetics of Drug Transporters: P-Glycoprotein and Solute Carrier Transporters

The pharmacogenetics of drug transporters is increasingly recognized as a critical factor influencing interindividual variability in drug absorption, distribution, and elimination. These membrane-bound proteins regulate drugs' movement across cellular barriers by actively pumping them out (efflux) or facilitating their uptake (influx). Among the major transporter families, ATP-binding cassette (ABC) and solute carrier (SLC) transporters play particularly prominent roles. Genetic polymorphisms...