Characterization of elongation factor-1A (eEF1A-1) and eEF1A-2/S1 protein expression in normal and wasted mice.
The eEF1Alpha-2 gene (S1) encodes a tissue-specific isoform of peptide elongation factor-1A (eEF1A-1); its mRNA is expressed only in brain, heart, and skeletal muscle, tissues dominated by terminally differentiated, long-lived cells. Homozygous mutant mice exhibit muscle wasting and neurodegeneration, resulting in death around postnatal day 28. eEF1Alpha-2/S1 protein shares 92% identity with eEF1A-1; because specific antibodies for each were not available previously, it was difficult to study the developmental expression patterns of these two peptide elongation factors 1A in wasted and wild-type mice. We generated a peptide-derived antiserum that recognizes the eEF1Alpha-2/S1 isoform and does not cross-react with eEF1A-1. We characterized the expression profiles of eEF1A-1 and eEF1A-2/S1 during development in wild-type (+/+), heterozygous (+/wst), and homozygous (wst/wst) mice. In wild-type and heterozygous animals, eEF1A-2/S1 protein is present only in brain, heart, and muscle; the onset of its expression coincides with a concomitant decrease in the eEF1A-1 protein level. In wasted mutant tissues, even though eEF1A-2/S1 protein is absent, the scheduled decline of eEF1A-1 occurs nonetheless during postnatal development, as it does in wild-type counterparts. In the brain of adult wild-type mice, the eEF1A-2/S1 isoform is localized in neurons, whereas eEF1A-1 is found in non-neuronal cells. In neurons prior to postnatal day 7, eEF1A-1 is the major isoform, but it is later replaced by eEF1A-2/S1, which by postnatal day 14 is the only isoform present. The postdevelopmental appearance of eEF1A-2/S1 protein and the decline in eEF1A-1 expression in brain, heart, and muscle suggest that eEF1A-2/S1 is the adult form of peptide elongation factor, whereas its sister is the embryonic isoform, in these tissues. The absence of eEF1A-2/S1, as well as the on-schedule development-dependent disappearance of its sister gene, eEF1A, in wst/wst mice may result in loss of protein synthesis ability, which may account for the numerous defects and ultimate fatality seen in these mice.
Khalyfa
A
A
Bloomfield Center for Research in Aging, Lady Davis Institute for Medical Research, The Sir Mortimer B. Davis-Jewish General Hospital, McGill University, Montréal, Québec H3T 1E2, Canada.
Bourbeau
D
D
Chen
E
E
Petroulakis
E
E
Pan
J
J
Xu
S
S
Wang
E
E
D000368:Aged; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D019084:Fluorescent Antibody Technique, Indirect; D006579:Heterozygote; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D020648:Peptide Elongation Factor 1 / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D020033:Protein Isoforms / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism
D017931:DNA Primers; D020648:Peptide Elongation Factor 1; D020033:Protein Isoforms; D011994:Recombinant Proteins; C000606749:eEF1A-1 protein, mouse