Determination of intrinsic creatine transporter (SLC6A8) activity and creatine transport function of leukocytes in rats

Ayaka Taii, Masanori Tachikawa, Yusuke Ohta, Kenichi I. Hosoya, Tetsuya Terasaki

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

Creatine transporter (CRT) deficiency (CRT-D) results in a significant reduction of brain creatine levels, which causes various neurological symptoms in early childhood, and diagnosis of the severity of CRT-D based on the residual CRT transport activity in liquid biopsy samples would be beneficial for early intervention. The apparent reduction in creatine transport activity in CRT-D is thought to be due to reduced intrinsic CRT-mediated creatine transport per CRT protein and/or reduced absolute CRT protein expression on the plasma membranes. The purpose of this study was thus to determine the normal level of intrinsic CRT-mediated creatine transport activity based on absolute CRT protein quantification using rat CRT-overexpressing HEK293 cells (CRT/HEK293 cells), and to clarify creatine transport in erythrocyte- and leukocyte-enriched fractions isolated from the circulating blood of rats. The intrinsic creatine transport rate was calculated to be 0.237µL/(min·fmol CRT) based on the initial uptake rate and the absolute CRT protein level in CRT/ HEK293 cells. Taking into account Avogadro’s constant, the creatine transport activity per CRT protein is estimated to be 1190 creatine/(min·CRT molecule) in the presence of [14C]creatine at an extracellular concentration of 5µM. Isolated leukocyte-enriched fraction exhibited mRNA expression of CRT and partially Na+dependent [14C]creatine transport, whereas erythrocytes showed neither. These characteristics suggest that the leukocytes contain the CRT-mediated creatine uptake system, and are available for evaluation of residual CRT transport activity in CRT-D patients.

Original languageEnglish
Pages (from-to)474-479
Number of pages6
JournalBiological and Pharmaceutical Bulletin
Volume43
Issue number3
DOIs
Publication statusPublished - 2020 Mar 1

Keywords

  • Creatine transporter
  • Creatine transporter deficiency
  • Diagnosis
  • Intrinsic transport activity
  • Leukocyte
  • Quantitative targeted absolute proteomics

ASJC Scopus subject areas

  • Pharmacology
  • Pharmaceutical Science

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