We have previously reported the posttranslational addition of [C-14]-argini
ne in the N-terminus of several soluble rat brain proteins, One of these pr
oteins was identified as the microtubule-associated protein, the stable tub
ule only polypeptide (STOP). However, despite the fact that the biological
significance of arginylation is not completely understood, some evidence as
sociates it with proteolysis via the ubiquitin pathway. Since this degradat
ive via is exacerbated as a response to stress, we studied in vitro the pos
ttranslational [C-14]-arginylation of cytosolic brain proteins of rats subj
ected to hyperthermia in vivo. Immediately after subjecting the animals to
hyperthermia, a minor reduction (16%) in the acceptor capacity of [C-14]arg
inine into proteins was observed in comparison with animals maintained at 2
8 degrees C, However, in the animals allowed to recover for 3 h, an increas
e (46%) in the arginylation was observed concomitantly with a significant a
ccumulation of the heat shock protein (70 kDa; hsp 70) when compared to the
control animals. These findings suggest that the posttranslational arginyl
ation of proteins participate in the heat shock response. The STOP protein
of the soluble brain fraction of control animals, which in Western blot app
ears as a doublet band (125 and 130 kDa, respectively), is seen, after the
hyperthermic treatment, as a single band of 125 kDa, The amount of 125 kDa
protein, as well as the in vitro incorporation of [C-14]-arginine, increase
s after hyperthermia in comparison with control animals. Following hyperthe
rmic treatment, we observed a decrease in the amount of in vivo [S-35]-meth
ionine-labeled brain proteins. We speculate that, as observed for STOP prot
ein, the increase in the degradation of protein that occurs in hyperthermia
, would produce an increase in the amount of arginine acceptor proteins, J.
Neurosci. Res. 56:85-92, 1999. (C) 1999 Wiley-Liss, Inc.