AbstractWe have previously reported thatDrosophilaKc cells require glutamine for maximal expression of heat shock proteins in stressed conditions (Sanders and Kon:J. Cell. Physiol.146:180–190, 1991). The mechanism of this effect has been investigated by comparing the metabolic utilization of glutamine in conditions which support hsp expression with that of glutamate in conditions where up to 100‐fold less hsp is synthesized. This comparison showed that free ammonia was generated by cells incubated in the presence of glutamine in 37°C (heat shock) conditions, but not at 25°C, and not in the presence of glutamate in either normal or heat shock conditions. There was no difference in the amount of 14CO2generated from either 14C‐labeled amino acid in the tricarboxylic acid cycle, but three‐ to four‐fold more alanine was synthesized in cells incubated in glutamine than in glutamate. Treating the cells with aminotransferase inhibitors to artificially increase NH3release raised hsp expression in the presence of glutamate to maximal levels characteristic of glutamine. This potentiation correlated with inhibition of alanine aminotransferase. Since only NH3production correlated with hsp expression in heat shock conditions in the presence of glutamine, and NH3addition to glutamate also resulted in maximal hsp expression, we measured glutamine production in glutamate plus NH3and observed net glutamine synthesis. The supposition that glutamine itself is responsible for the regulatory changes supporting maximal hsp expression was supported by the finding that the glutamine analog, 6‐diazo‐5‐oxo‐L‐norleucine (DON), mimicked the effects of glutamine. We conclude that glutamine imposes regulatory changes which alter nitrogen metabolism and support hsp e
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