Journal of Lipid Research, Vol 26, 1421-1430, Copyright © 1985 by Lipid Research, Inc.
Plasma and hepatic apoE isoproteins of nonhuman primates. Differences in apoE among humans, apes, and New and Old World monkeys
VI Zannis, RJ Nicolosi, E Jensen, JL Breslow and KC Hayes
We have used two-dimensional polyacrylamide gel electrophoresis (PAGE) to
study the plasma and hepatic apoE isoproteins of nonhuman primates and have
compared them with their human counterparts. We have found that apoE
obtained from fresh monkey or ape plasma, as well as nascent apoE
synthesized by perfused monkey livers, is composed of several isoproteins
that resemble the homozygous (beta) apoE phenotype observed in humans. The
nonhuman primate plasma apoE pattern of 90 animals from nine different
species consisted of a major isoprotein designated apoE3 and a few minor
isoproteins. A group of acidic apoE isoproteins is eliminated after
treatment with C. perfringens neuraminidase and has been designated sialo
apoE (apoEs). Nonhuman primate liver apoE isoproteins comigrate with their
plasma apoE isoprotein counterparts on two-dimensional PAGE, but hepatic
apoE is enriched in sialo apoE isoproteins when compared to plasma apoE.
The apparent molecular weight of asialo and sialo apoE obtained from Old
World monkeys and apes is identical to the molecular weight of the
corresponding human isoproteins (E3 = 38K, Es = 38.5-39.5K). However, the
apparent molecular weight of apoE isoproteins obtained from New World
monkeys is increased by approximately 0.5K (E3 = 38.5K, Es = 39.0-40.0K) as
compared to the molecular weight of human and Old World monkey and ape
isoproteins. The isoelectric points of apoE3 obtained from Old World
monkeys, New World monkeys, chimpanzees, and gibbons are 5.74, 5.76, 5.95,
and 5.89, respectively. The entire New or Old World monkey, chimpanzee, and
gibbon apoE pattern is shifted by approximately -2.0, - 0.5, and -1.0
charges, respectively, relative to the pattern of the corresponding human
E3/3 phenotype. The molecular weight difference in apoE observed among New
and Old World monkeys, as well as the molecular weight and/or charge
differences observed among monkey, ape, and human apoE are consistent with
structural changes in the apoE gene which have occurred following the
divergence of the different species. The observation of only the homozygous
apoE phenotypes in all animals studied suggests that the common apoE
genetic polymorphism recently described in humans may not be present in
nonhuman primates.
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