Posttranslational arginylation of soluble rat brain proteins after whole body hyperthermia

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.