EXPRESSION OF ELONGATION FACTOR-1-ALPHA AND S1 IN YOUNG AND OLD HUMANSKELETAL-MUSCLE

Previous research has indicated that reduced expression of elongation factor-1 alpha (EF-1 alpha) may be an important determinant of the red uced rate of protein synthesis in senescent animals and cultured cells . The present study examined whether expression of EF-1 alpha or S1, a homologous protein found exclusively in postmitotic tissues, is reduc ed in senescent human skeletal muscle. Muscle biopsies were obtained f rom the vastus lateralis muscles of healthy young (22-31 yr old) and o ld (61-74 yr old) subjects. As reported previously, myofibrillar prote in synthesis was similar to 40% slower in the older muscle (p < .001) as determined by incorporation of a stable isotope. Immunoblotting rev ealed no difference in the concentration of EF-1 alpha + S1 between yo unger and older muscle. RT-PCR assays indicated that SI mRNA was much more abundant than EP-1 alpha mRNA in muscles of both age groups, with no reduction in either EF-1 alpha or SI mRNA abundance in older muscl es. We conclude that expression of EF-1 alpha and SI is not diminished in older muscles and does not explain the age-related slowing of prot ein synthesis in human skeletal muscle. However, we cannot exclude the possibility that the activity of these proteins declines during senes cence due to post-translational modifications.