Myocellular creatine and creatine transporter serine phosphorylation after starvation

Chun Rui Zhao, Lihong Shang, Weiyang Wang, Danny O. Jacobs

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

Background. Myocellular creatine, which is critically important for normal energy metabolism, increases in rat gastrocnemius muscle after starvation via unknown mechanisms. Creatine (Cr) uptake across plasma membranes is governed by a single, specific transporter (CrTr) that shares 50% amino acid sequence identity with GABA/choline/betaine transporters whose functions are modulated by phosphorylation. Methods. Gastrocnemius muscle was collected from adult male Sprague-Dawley (225-250 g) rats that were randomized to receive normal rat chow and distilled water ad libitum (CTL) or distilled water alone for 4 days (STV). Total Cr, phosphocreatine (PCr), free Cr, and ATP were measured luminometrically. CrTr protein expression and protein serine and tyrosine phosphorylation and mRNA expression were determined using immunoprecipitation and quantitative Western blotting and reverse transcription polymerase chain reaction (RT-PCR) analyses, respectively. Guanidinoacetate methyltransferase (GAMT) activity, guanidinoacetic acid (GAA) content, creatine kinase (CK) activity, and creatinine (Crn) content were assayed luminometrically or spectrophotometrically. Creatine transporter uptake activity was also measured in skeletal muscle membrane vesicles. Data were analyzed by t test. Results. Total Cr and free Cr increased 26 and 280% in STV (32.3 ± 1.0 and 12.9 ± 1.4 vs 25.7 ± 1.1 and 3.4 ± 0.9 μmol/g wet wt, mean ± SEM, respectively, P < 0.01) whereas PCr content decreased 18% (18.6 ± 0.8 vs 22.8 ± 0.9 μmol/g wet wt, STV vs CTL P < 0.05). CrTr protein and mRNA expression, ATP, GAA, CK, GAMT, and protein tyrosine phosphorylation of CrTr were not significantly different between the two groups. However, protein serine phosphorylation of CrTr was significantly reduced by 30% (P < 0.05) and creatine uptake activity was significantly increased (P < 0.05) in starved animals. Conclusion. Increases in myocellular creatine content after starvation are associated with reduced serine phosphorylation of the creatine transporter.

Original languageEnglish (US)
Pages (from-to)10-16
Number of pages7
JournalJournal of Surgical Research
Volume105
Issue number1
DOIs
StatePublished - Jan 1 2002

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Keywords

  • Creatine kinase
  • Creatine transporter
  • Creatine uptake
  • Guanidinoacetate methyltransferase
  • Guanidinoacetic acid
  • Luminometry
  • Protein phosphorylation
  • Skeletal muscle membrane vesicle
  • Starvation

ASJC Scopus subject areas

  • Surgery

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