title: The glutamate agonist homocysteine sulfinic acid stimulates glucose uptake through the calcium-dependent AMPK-p38 MAPK-protein kinase C zeta pathway in skeletal muscle cells.
abstract: Homocysteine sulfinic acid (HCSA) is a homologue of the amino acid cysteine and a selective metabotropic glutamate receptor (mGluR) agonist. However, the metabolic role of HCSA is poorly understood. In this study, we showed that HCSA and glutamate stimulated glucose uptake in C2C12 mouse myoblast cells and increased AMP-activated protein kinase (AMPK) phosphorylation. RT-PCR and Western blot analysis revealed that C2C12 expresses mGluR5. HCSA transiently increased the intracellular calcium concentration. Although α-methyl-4-carboxyphenylglycine, a metabotropic glutamate receptor antagonist, blocked the action of HCSA in intracellular calcium response and AMPK phosphorylation, 6-cyano-7-nitroquinoxaline-2,3-dione, an AMPA antagonist, did not exhibit such effects. Knockdown of mGluR5 with siRNA blocked HCSA-induced AMPK phosphorylation. Pretreatment of cells with STO-609, a calmodulin-dependent protein kinase kinase (CaMKK) inhibitor, blocked HCSA-induced AMPK phosphorylation, and knockdown of CaMKK blocked HCSA-induced AMPK phosphorylation. In addition, HCSA activated p38 mitogen-activated protein kinase (MAPK). Expression of dominant-negative AMPK suppressed HCSA-mediated phosphorylation of p38 MAPK, and inhibition of AMPK and p38 MAPK blocked HCSA-induced glucose uptake. Phosphorylation of protein kinase C ζ (PKCζ) was also increased by HCSA. Pharmacologic inhibition or knockdown of p38 MAPK blocked HCSA-induced PKCζ phosphorylation, and knockdown of PKCζ suppressed the HCSA-induced increase of cell surface GLUT4. The stimulatory effect of HCSA on cell surface GLUT4 was impaired in FITC-conjugated PKCζ siRNA-transfected cells. Together, the above results suggest that HCSA may have a beneficial role in glucose metabolism in skeletal muscle cells via stimulation of AMPK.
authors.affiliation: Department of Anatomy, Korea University College of Medicine, Seoul 136-701, Korea.
authors.forename: Ji Hae
authors.initials: JH
authors.lastname: Kim
authors.forename: Jung Ok
authors.initials: JO
authors.lastname: Lee
authors.forename: Soo Kyung
authors.initials: SK
authors.lastname: Lee
authors.forename: Ji Wook
authors.initials: JW
authors.lastname: Moon
authors.forename: Ga Young
authors.initials: GY
authors.lastname: You
authors.forename: Su Jin
authors.initials: SJ
authors.lastname: Kim
authors.forename: Sun-Hwa
authors.initials: SH
authors.lastname: Park
authors.forename: Ji Man
authors.initials: JM
authors.lastname: Park
authors.forename: Se Young
authors.initials: SY
authors.lastname: Lim
authors.forename: Pann-Ghill
authors.initials: PG
authors.lastname: Suh
authors.forename: Kyung-Ok
authors.initials: KO
authors.lastname: Uhm
authors.forename: Min Seok
authors.initials: MS
authors.lastname: Song
authors.forename: Hyeon Soo
authors.initials: HS
authors.lastname: Kim
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D005947:Glucose / Q000493:pharmacokinetics*; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D006710:Homocysteine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D051379:Mice; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D018482:Muscle, Skeletal / Q000166:cytology / Q000201:enzymology; D010766:Phosphorylation / Q000502:physiology; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate / Q000235:genetics / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D000099221:Protein Kinase C zeta
chemical_list: D002118:Calcium; D054737:Calcium-Calmodulin-Dependent Protein Kinase Kinase; D005947:Glucose; D051275:Glucose Transporter Type 4; D006710:Homocysteine; D011493:Protein Kinase C; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate; D048051:p38 Mitogen-Activated Protein Kinases; D000099221:Protein Kinase C zeta; C578936:Grm5 protein, mouse; C495693:Slc2a4 protein, mouse; C010982:homocysteinesulfinic acid