Regulatory mechanisms of SNAT2,an amino acid transporter,in L6 rat skeletal muscle cells by insulin,osmotic shock and amino acid deprivation

摘要

Several studies have demonstrated that the activity of system A is upregulated by insulin,osmotic shock and amino acid deprivation.However,the mechanisms are not clear.We carried out studies using L6 rat skeletal muscle cells to clarify the mechanisms of upreg-ulation of system A activity by insulin,osmotic shock and amino acid deprivation.The upregulation was found to be due to an increase in V_(max),not K_m.Chloroquine and wortmannin inhibited the upregulation induced by insulin stimulation and amino acid deprivation but not that induced by osmotic shock.On the other hand,cycloheximide and actinomycin D inhibited the upregulation by each stimulation.Moreover,PD98059 and SP600125 inhibited only amino acid deprivation-induced upregulation and SB202190 inhibited only insulin-induced upregulation.Our findings indicate that the mechanisms of upregulation of system A activity by insulin,osmotic shock and amino acid deprivation are different in L6 cells.Western blot and RT-PCR analysis showed an increase in system A at the protein and mRNA levels with each stimulation.