Metabolic cooperation between human fibroblasts with normal and with mutant superactive phosphoribosylpyrophosphate synthetase

METABOLIC cooperation is a form of intercellular communication by which cells in contact exchange molecules, a process providing multicellular organisms with an important mechanism for control of metabolic activity¹. Subak-Sharpe et al.² observed contact-dependent transfer of purine nucleotides from normal cells to cells mutationally incapable of producing inosinic acid due to deficiency in hypoxanthine-guanine phosphoribosyl- transferase³. Metabolic cooperation of this type was later also demonstrated with other enzymic markers, such as adenine phosphoribosyltransferase and thymidine kinase^4,5. Such transfers are characterised, by the normal cell being the donor and the mutant cell being the recipient, the former transferring to the latter a mutationally lacking metabolite. We report here on a new form of contact-dependent metabolic cooperation, unique in that the transfer of a metabolite occurs from a mutant donor cell to a normal recipient cell.