Facilitated transport of methotrexate polyglutamates into lysosomes derived from S180 cells: Further characterization and evidence for a simple mobile carrier system with broad specificity for homo- or heteropeptides bearing a C-terminal glutamyl moiety Journal Article
| Authors: | Barrueco, J. R.; O'Leary, D. F.; Sirotnak, F. M. |
| Article Title: | Facilitated transport of methotrexate polyglutamates into lysosomes derived from S180 cells: Further characterization and evidence for a simple mobile carrier system with broad specificity for homo- or heteropeptides bearing a C-terminal glutamyl moiety |
| Abstract: | Studies are presented further characterizing a facilitative system transporting methotrexate (MTX) polyglutamates into lysosomes derived from S180 cells. Initial influx of [3H]MTX + G1 (MTX with 1 additional glutamyl residue) exhibited a slightly alkaline pH optimum (pH 7.7) and was moderately temperature-dependent (Q10 27-37°C = 3.1 ± 0.1). An analysis of the kinetics of intralysosomal accumulation of [3H]MTX + G1 showed saturation kinetics for initial influx, but linear kinetics for the steady-state level of exchangeable [3H]MTX + G1 at different external concentrations of [3H]MTX + G1. In addition, the system exhibited substantial directional asymmetry with respect to the interaction with MTX + G1 during influx and efflux. Accelerated homo- and heteroexchange diffusion was demonstrated for influx of [3H]MTX + G1, while decelerated homoexchange diffusion was demonstrated for efflux of [3H]MTX + G1 following trans-positioning of MTX + G1 or glutamyl-γ-glutamate in the opposite compartment. These observations were consistent with a single mobile carrier system mediating influx and efflux of this polyglutamate. Based upon an analysis of competitive interactions with [3H] MTX + G1, this system displayed specificity for MTX-γ-glutamates, folyl-γ-polyglutamates, α- or γ-glutamyl peptides and heteropeptides bearing a C-terminal γ-glutamate but not for MTX or glutamate, themselves. Among polyglutamates, γ-glutamyl chain length was not a significant factor for transport except in the case of MTX polyglutamates. Overall, our results appear to delineate in the lysosomal membrane a simple mobile carrier system with broad specificity for folyl- or non-folyl-bearing peptides responsible for the transport of MTX polyglutamates. |
| Keywords: | controlled study; nonhuman; methotrexate; mouse; animal; mice; intracellular transport; mice, inbred c57bl; kinetics; drug accumulation; drug uptake; temperature; glutamic acid; glutamates; drug transport; membrane transport; glutamine; drug diffusion; hydrogen-ion concentration; lysosome; lysosome membrane; lysosomes; tritium; binding, competitive; polyglutamic acid; biological transport, active; mice, inbred dba; active transport; priority journal; article; support, non-u.s. gov't; support, u.s. gov't, p.h.s.; sarcoma 180; methotrexate polyglutamate |
| Journal Title: | Journal of Biological Chemistry |
| Volume: | 267 |
| Issue: | 28 |
| ISSN: | 0021-9258 |
| Publisher: | American Society for Biochemistry and Molecular Biology |
| Date Published: | 1992-10-05 |
| Start Page: | 19986 |
| End Page: | 19991 |
| Language: | English |
| PUBMED: | 1383199 |
| PROVIDER: | scopus |
| DOI/URL: | |
| Notes: | Article -- Source: Scopus |
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