Dataset Information

Bis(benzyl)polyamine analogues are substrates for a mammalian cell-transport system which is distinct from the polyamine-transport system.

ABSTRACT: Bis(benzyl)polyamine analogues (e.g. NN'-bis(3-[(phenylmethyl)amino]propyl)-1,8-diamino-octane [C6H5CH2NH-(CH2)3NH(CH2)8NH(CH2)3NHCH2C6H5]) have previously been shown to regulate polyamine biosynthesis and growth of rat hepatoma (HTC) cells. Saturable uptake of the analogues, the ability of other bis(benzyl)polyamine analogues to compete for this uptake and the trans-acceleration of this uptake in pre-loaded cells indicate that these novel compounds are accumulated through the action of a transport system in HTC cells. A mutant Chinese-hamster-ovary (CHO) cell line, CHOMG, which lacks a functional polyamine-transport system, exhibited saturable bis(benzyl)polyamine uptake identical with that observed in the parental CHO cells, which have normal polyamine transport. The uptake of the analogue by both CHOMG and CHO cells was competitively inhibited by other bis(benzyl)polyamine analogues, but was insensitive to excess spermine. Treatment with alpha-difluoromethylornithine, an inhibitor of polyamine biosynthesis, resulted in the enhancement of spermine uptake in CHO cells but did not alter the uptake of a bis(benzyl)polyamine analogue by either CHO or CHOMG cells. Thus it appears that bis(benzyl)polyamine analogues are substrates for a mammalian-cell-transport system distinct from the polyamine-transport system.

SUBMITTER: Byers TL

PROVIDER: S-EPMC1131527 | biostudies-other | 1990 Jul

REPOSITORIES: biostudies-other

ACCESS DATA

Similar Datasets

Project description:Mammalian polyamine transporters have not thus far been biochemically characterized. Since essential carboxy groups in the polyamine carrier might participate in the transport process, the ability of two different carbodi-imides to affect [3H]spermidine uptake was assessed in Chinese hamster ovary cells. Both the hydrophobic 1,3-dicyclohexylcarbodi-imide (DCC) and the more polar 1-ethyl-3-(3-dimethylaminopropyl)carbodi-imide (EDC) irreversibly inhibited spermidine transport with EC50 values of 11 +/- 4 and 96 +/- 16 microM after 30 min at 22 degrees C respectively. Prior treatment with EDC in the absence of substrate decreased both the Vmax and K(m) for spermidine uptake in a time- and concentration-dependent manner. Spermidine-transport inactivation by EDC (1 mM) was temperature-dependent, with 60 and 90% inhibition observed after 10 min at 22 and 37 degrees C respectively. Spermine (10 microM) almost fully protected against spermidine-transport inactivation by EDC at 22 degrees C, and decreased the rate of inactivation at 37 degrees C by about 80%. Putrescine, spermidine and spermine were all effective in protecting against EDC-mediated inactivation of [3H]spermidine and [3H]putrescine uptake at 22 degrees C with EC50 values estimated at 10, 1 and less than 1 microM respectively. The nucleophile glycine ethyl ester (up to 50 mM) prevented the inhibition brought about by 1 mM EDC. Inhibition by 1 mM EDC was greater at pH 7.2 than at pH 5.8 (89 +/- 3 compared with 44 +/- 5%), whereas the converse was true for 100 microM DCC (81 +/- 3 compared with 92 +/- 5%). On the other hand, spermine did not protect against inactivation of spermidine uptake by DCC. Moreover, DCC, but not EDC, inhibited Na(+)-dependent amino acid uptake. The present data indicate that (i) EDC and DCC inhibit polyamine transport through distinct mechanisms, (ii) substrate binding occludes one or several carboxy groups lying in a polar environment of the carrier and (iii) these carboxyl residues might be activated by EDC to crosslink a neighbouring nucleophile side group, resulting in a conformation of the polyamine carrier which is inactive for transport.

Dataset Information

Bis(benzyl)polyamine analogues are substrates for a mammalian cell-transport system which is distinct from the polyamine-transport system.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets