Chronic ethanol exposure in rats affects rabs-dependent hepatic trafficking of apolipoprotein E and transferrin.
Because of the important roles of rabs in protein trafficking, we tested whether chronic ethanol exposure affected the trafficking of newly synthesized apolipoprotein E (apoE) or transferrin (O-glycosylated and N-glycosylated proteins, respectively) attached to acylated or prenylated rabs. The in vivo 30-min incorporation ratios of [3H]palmitate:[35S]methionine or [3H]mevalonate:[35S]methionine (relative ratios of rabs acylation or prenylation to total protein or to immunoisolated apoE or transferrin) were measured in various hepatic subcellular organelles of 8 week-ethanol-fed (E) and pair-fed control (C) Wistar-Furth rats. With respect to total protein trafficking, ethanol increased rabs acylation ratio by 136% (P <.01), 69% (P <.05), and 64% (P <.01) in the endoplasmic reticulum (ER), Golgi light fraction (GLF), and Golgi heavy fraction (GHF), respectively, and decreased this ratio by 76% (P <.01) in carrier vesicle fraction 2 (CV2). With respect to apoE trafficking, ethanol increased rabs acylation ratio by 121% in GHF and decreased this ratio by 27% in CV2. Rabs prenylation ratio increased by 21% and 53% in GHF and CV2, respectively, and decreased by 42% in GLF. With respect to transferrin trafficking, ethanol increased rabs acylation ratio by 53% (P <.01) in GHF, with no significant effect in ER, whereas rabs prenylation ratio increased by 26% (P <.05) in ER, with no significant effect in GHF. Therefore, we conclude that ethanol-induced impaired trafficking of newly synthesized O- and N-glycosylated proteins occurs primarily in ER and Golgi and is due to altered lipidation of rabs, possibly rabs 1, 2, or 6 or combinations of these three rabs.
Marmillot
P
P
Lipid Research Laboratory, DVA Medical Center, Washington, DC 20422, USA.
Rao
M N
MN
Lakshman
M R
MR
D000818:Animals; D001057:Apolipoproteins E / Q000378:metabolism*; D002492:Central Nervous System Depressants / Q000494:pharmacology*; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D000431:Ethanol / Q000494:pharmacology*; D006056:Golgi Apparatus / Q000187:drug effects / Q000378:metabolism; D007424:Intracellular Fluid / Q000378:metabolism; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D051381:Rats; D011920:Rats, Inbred WF; D014168:Transferrin / Q000378:metabolism*; D020691:rab GTP-Binding Proteins / Q000502:physiology*
D001057:Apolipoproteins E; D002492:Central Nervous System Depressants; D014168:Transferrin; D000431:Ethanol; D020691:rab GTP-Binding Proteins