TY - JOUR
T1 - Muscle contractions, AICAR, and insulin cause phosphorylation of an AMPK-related kinase
AU - Fisher, Jonathan S.
AU - Ju, Jeong Sun
AU - Oppelt, Peter J.
AU - Smith, Jill L.
AU - Suzuki, Atsushi
AU - Esumi, Hiroyasu
PY - 2005/12
Y1 - 2005/12
N2 - We hypothesized that AMP-activated protein kinase-related kinase 5 (ARK5)/novel kinase family 1 (NUAK1), an AMP-activated protein kinase (AMPK)-related kinase that has been found to be stimulated by protein kinase B (Akt), would be expressed in rat skeletal muscle and activated by electrically elicited contractions, 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR), or insulin. We verified expression of ARK5 in muscle through RT-PCR and Western blot. Cross-reactivity of ARK5 immunoprecipitates with antibodies against phospho-AMPK was increased by ∼30% by muscle contractions and ∼60% by incubation of muscle with AICAR. AMPK was not detected in the ARK5 immunoprecipitates. Despite the apparent increase in phosphorylation of ARK5 at a site essential to its activation, neither contractions nor AICAR increased ARK5 activity. For muscles from animals injected with saline or insulin, we probed nonimmunoprecipitated samples in sequence for phosphotyrosine (P-Tyr), ARK5, and phosphorylated substrates of Akt (P-AS) and found that the ARK5 band could be precisely superimposed on phosphoprotein bands from the P-Tyr and P-AS blots. In the band corresponding to ARK5, insulin increased P-Tyr content by ∼45% and cross-reactivity with the antibody against P-AS by approximately threefold. We also detected ARK5 in phosphotyrosine immunoprecipitates. Our data suggest that increased phosphorylation of ARK5 by muscle contractions or exposure to AICAR is insufficient to activate ARK5 in skeletal muscle, suggesting that some other modification (e.g., phosphorylation on tyrosine or by Akt) may be necessary to its activity in muscle.
AB - We hypothesized that AMP-activated protein kinase-related kinase 5 (ARK5)/novel kinase family 1 (NUAK1), an AMP-activated protein kinase (AMPK)-related kinase that has been found to be stimulated by protein kinase B (Akt), would be expressed in rat skeletal muscle and activated by electrically elicited contractions, 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR), or insulin. We verified expression of ARK5 in muscle through RT-PCR and Western blot. Cross-reactivity of ARK5 immunoprecipitates with antibodies against phospho-AMPK was increased by ∼30% by muscle contractions and ∼60% by incubation of muscle with AICAR. AMPK was not detected in the ARK5 immunoprecipitates. Despite the apparent increase in phosphorylation of ARK5 at a site essential to its activation, neither contractions nor AICAR increased ARK5 activity. For muscles from animals injected with saline or insulin, we probed nonimmunoprecipitated samples in sequence for phosphotyrosine (P-Tyr), ARK5, and phosphorylated substrates of Akt (P-AS) and found that the ARK5 band could be precisely superimposed on phosphoprotein bands from the P-Tyr and P-AS blots. In the band corresponding to ARK5, insulin increased P-Tyr content by ∼45% and cross-reactivity with the antibody against P-AS by approximately threefold. We also detected ARK5 in phosphotyrosine immunoprecipitates. Our data suggest that increased phosphorylation of ARK5 by muscle contractions or exposure to AICAR is insufficient to activate ARK5 in skeletal muscle, suggesting that some other modification (e.g., phosphorylation on tyrosine or by Akt) may be necessary to its activity in muscle.
KW - Novel kinase family 1
KW - Novel kinase family 2
KW - Phosphotyrosine
KW - Protein kinase B
KW - Sucrose nonfermenting protein kinase/AMP-activated protein kinase-related protein kinase
UR - http://www.scopus.com/inward/record.url?scp=33644664089&partnerID=8YFLogxK
U2 - 10.1152/ajpendo.00335.2004
DO - 10.1152/ajpendo.00335.2004
M3 - Article
C2 - 16030062
AN - SCOPUS:33644664089
SN - 0193-1849
VL - 289
SP - E986-E992
JO - American Journal of Physiology - Endocrinology and Metabolism
JF - American Journal of Physiology - Endocrinology and Metabolism
IS - 6
ER -