Age-related increase of insoluble, phosphorylated small heat shock proteins in human skeletal muscle.
Among mammalian heat shock proteins (Hsps), small Hsps (sHsps) are constitutively expressed in skeletal muscles. We investigated age-related changes of phosphorylation and cellular distribution of representative sHsps (Hsp27 and alphaB-crystallin) in human vastus lateralis muscle under resting conditions. We also examined upstream kinases which may be responsible for phosphorylation of sHsps, namely p38 mitogen-activated protein kinase (MAPK), MAPK-activated protein kinase-2, and extracellular signal-regulated kinase-1/2. The study groups consisted of nine young (15-38 years old) and nine aged (51-79 years old) patients who underwent orthopedic surgery. sHsps protein levels were higher in the insoluble fraction of aged muscles. The phosphorylated states of sHsps were enhanced in both the soluble and insoluble fraction of aged patients. The phosphorylated form of each upstream kinase was elevated in aged patients. Ubiquitinated proteins accumulated in the insoluble fractions of aged muscles. Aging mechanisms may affect the activation process of MAPKs, and the phosphorylation and accumulation of sHsps.
Yamaguchi
Tetsuo
T
Department of Life Sciences, The Graduate School of Arts and Sciences, The University of Tokyo, Japan.
Arai
Hideaki
H
Katayama
Naoki
N
Ishikawa
Tomoji
T
Kikumoto
Kiyoshi
K
Atomi
Yoriko
Y
D000293:Adolescent; D000328:Adult; D000368:Aged; D000375:Aging / Q000378:metabolism*; D015153:Blotting, Western; D004591:Electrophoresis, Polyacrylamide Gel; D050888:Heat-Shock Proteins, Small / Q000378:metabolism*; D006801:Humans; D008875:Middle Aged; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction
D050888:Heat-Shock Proteins, Small; D020928:Mitogen-Activated Protein Kinases