Amino acid deprivation-induced stress response in the bovine renal epithelial cell line NBL-1: induction of HSP 70 by phenylalanine.
Amino acid deprivation of the bovine renal epithelial cell line NBL-1 led to a range of responses by the heat shock and glucose regulated stress proteins. The classic heat shock induction of HSP 72 was found to be mimicked, without prior heat stress, by phenylalanine addition to cells simultaneously deprived of all other amino acids. Co-inclusion of alanine prevented the HSP 72 induction by phenylalanine but not that caused by heat stress. Phenylalanine also increased expression of HSP 70 mRNA in cells simultaneously deprived of other amino acids. The glucose regulated protein GRP 75 was increased upon amino acid deprivation. GRP94 was detectable in a 50 kDa form in control cells but was detected as a 94 kDa form upon amino acid deprivation which was further enhanced upon inclusion of phenylalanine. Addition of alanine to the starvation medium led to detection of the 50 kDa form only. Amino acid deprivation appears to mimic the glucose deprivation stress response. Inclusion of phenylalanine during amino acid deprivation leads to a stress response similar to that of heat shock in terms of HSP 72 induction. However, the two inducers are sensitive to different repression signals since only the phenylalanine-signal was subject to nihilation by alanine co-inclusion.