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. 1995 Dec 1;131(5):1173–1182. doi: 10.1083/jcb.131.5.1173

Transferrin-binding protein complex is the receptor for transferrin uptake in Trypanosoma brucei

PMCID: PMC2120630  PMID: 8522581

Abstract

In Trypanosoma brucei, the products of two genes, ESAG 6 and ESAG 7, located upstream of the variant surface glycoprotein gene in a polycistronic expression site form a glycosylphosphatidylinositol- anchored transferrin-binding protein (TFBP) complex. It is shown by gel filtration and membrane-binding experiments that the TFBP complex is heterodimeric and binds one molecule of transferrin with high affinity (2,300 binding sites per cell; KD = 2.1 nM for the dominant expression site from T. brucei strain 427 and KD = 131 nM for ES1.3A of the EATRO 1125 stock). The ternary transferrin-TFBP complexes with iron-loaded or iron-free ligand are stable between pH 5 and 8. Cellular transferrin uptake can be inhibited by 90% with Fab fragments from anti-TFBP antibodies. After uptake, the TFBP complex and its ligand are routed to lysosomes where transferrin is proteolytically degraded. While the degradation products are released from the cells, iron remains cell associated and the TFBP complex is probably recycled to the membrane of the flagellar pocket, the only site for exo- and endocytosis in this organism. It is concluded that the TFBP complex serves as the receptor for the uptake of transferrin in T. brucei by a mechanism distinct from that in mammalian cells.

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Selected References

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  1. Alexandre S., Guyaux M., Murphy N. B., Coquelet H., Pays A., Steinert M., Pays E. Putative genes of a variant-specific antigen gene transcription unit in Trypanosoma brucei. Mol Cell Biol. 1988 Jun;8(6):2367–2378. doi: 10.1128/mcb.8.6.2367. [DOI] [PMC free article] [PubMed] [Google Scholar]
  2. Andrews P. The gel-filtration behaviour of proteins related to their molecular weights over a wide range. Biochem J. 1965 Sep;96(3):595–606. doi: 10.1042/bj0960595. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Balber A. E. The pellicle and the membrane of the flagellum, flagellar adhesion zone, and flagellar pocket: functionally discrete surface domains of the bloodstream form of African trypanosomes. Crit Rev Immunol. 1990;10(3):177–201. [PubMed] [Google Scholar]
  4. Baltz T., Baltz D., Giroud C., Crockett J. Cultivation in a semi-defined medium of animal infective forms of Trypanosoma brucei, T. equiperdum, T. evansi, T. rhodesiense and T. gambiense. EMBO J. 1985 May;4(5):1273–1277. doi: 10.1002/j.1460-2075.1985.tb03772.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Borst P., Rudenko G. Antigenic variation in African trypanosomes. Science. 1994 Jun 24;264(5167):1872–1873. doi: 10.1126/science.7516579. [DOI] [PubMed] [Google Scholar]
  6. Brickman M. J., Balber A. E. Transport of a lysosomal membrane glycoprotein from the Golgi to endosomes and lysosomes via the cell surface in African trypanosomes. J Cell Sci. 1994 Nov;107(Pt 11):3191–3200. doi: 10.1242/jcs.107.11.3191. [DOI] [PubMed] [Google Scholar]
  7. Chaudhri M., Steverding D., Kittelberger D., Tjia S., Overath P. Expression of a glycosylphosphatidylinositol-anchored Trypanosoma brucei transferrin-binding protein complex in insect cells. Proc Natl Acad Sci U S A. 1994 Jul 5;91(14):6443–6447. doi: 10.1073/pnas.91.14.6443. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Coppens I., Opperdoes F. R., Courtoy P. J., Baudhuin P. Receptor-mediated endocytosis in the bloodstream form of Trypanosoma brucei. J Protozool. 1987 Nov;34(4):465–473. doi: 10.1111/j.1550-7408.1987.tb03216.x. [DOI] [PubMed] [Google Scholar]
  9. Crichton R. R., Charloteaux-Wauters M. Iron transport and storage. Eur J Biochem. 1987 May 4;164(3):485–506. doi: 10.1111/j.1432-1033.1987.tb11155.x. [DOI] [PubMed] [Google Scholar]
  10. Cross G. A. Identification, purification and properties of clone-specific glycoprotein antigens constituting the surface coat of Trypanosoma brucei. Parasitology. 1975 Dec;71(3):393–417. doi: 10.1017/s003118200004717x. [DOI] [PubMed] [Google Scholar]
  11. Cully D. F., Ip H. S., Cross G. A. Coordinate transcription of variant surface glycoprotein genes and an expression site associated gene family in Trypanosoma brucei. Cell. 1985 Aug;42(1):173–182. doi: 10.1016/s0092-8674(85)80113-6. [DOI] [PubMed] [Google Scholar]
  12. Fernandez-Pol J. A., Klos D. J. Isolation and characterization of normal rat kidney cell membrane proteins with affinity for transferrin. Biochemistry. 1980 Aug 19;19(17):3904–3912. doi: 10.1021/bi00558a003. [DOI] [PubMed] [Google Scholar]
  13. Grab D. J., Shaw M. K., Wells C. W., Verjee Y., Russo D. C., Webster P., Naessens J., Fish W. R. The transferrin receptor in African trypanosomes: identification, partial characterization and subcellular localization. Eur J Cell Biol. 1993 Oct;62(1):114–126. [PubMed] [Google Scholar]
  14. Grab D. J., Wells C. W., Shaw M. K., Webster P., Russo D. C. Endocytosed transferrin in African trypanosomes is delivered to lysosomes and may not be recycled. Eur J Cell Biol. 1992 Dec;59(2):398–404. [PubMed] [Google Scholar]
  15. Hobbs M. R., Boothroyd J. C. An expression-site-associated gene family of trypanosomes is expressed in vivo and shows homology to a variant surface glycoprotein gene. Mol Biochem Parasitol. 1990 Nov;43(1):1–16. doi: 10.1016/0166-6851(90)90125-6. [DOI] [PubMed] [Google Scholar]
  16. Huebers H. A., Finch C. A. The physiology of transferrin and transferrin receptors. Physiol Rev. 1987 Apr;67(2):520–582. doi: 10.1152/physrev.1987.67.2.520. [DOI] [PubMed] [Google Scholar]
  17. Ilg T., Fuchs M., Gnau V., Wolfram M., Harbecke D., Overath P. Distribution of parasite cysteine proteinases in lesions of mice infected with Leishmania mexicana amastigotes. Mol Biochem Parasitol. 1994 Oct;67(2):193–203. doi: 10.1016/0166-6851(94)00126-x. [DOI] [PubMed] [Google Scholar]
  18. Karin M., Mintz B. Receptor-mediated endocytosis of transferrin in developmentally totipotent mouse teratocarcinoma stem cells. J Biol Chem. 1981 Apr 10;256(7):3245–3252. [PubMed] [Google Scholar]
  19. Klausner R. D., Ashwell G., van Renswoude J., Harford J. B., Bridges K. R. Binding of apotransferrin to K562 cells: explanation of the transferrin cycle. Proc Natl Acad Sci U S A. 1983 Apr;80(8):2263–2266. doi: 10.1073/pnas.80.8.2263. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Kooter J. M., Winter A. J., de Oliveira C., Wagter R., Borst P. Boundaries of telomere conversion in Trypanosoma brucei. Gene. 1988 Sep 15;69(1):1–11. doi: 10.1016/0378-1119(88)90372-1. [DOI] [PubMed] [Google Scholar]
  21. Kooter J. M., van der Spek H. J., Wagter R., d'Oliveira C. E., van der Hoeven F., Johnson P. J., Borst P. The anatomy and transcription of a telomeric expression site for variant-specific surface antigens in T. brucei. Cell. 1987 Oct 23;51(2):261–272. doi: 10.1016/0092-8674(87)90153-x. [DOI] [PubMed] [Google Scholar]
  22. Lanham S. M., Godfrey D. G. Isolation of salivarian trypanosomes from man and other mammals using DEAE-cellulose. Exp Parasitol. 1970 Dec;28(3):521–534. doi: 10.1016/0014-4894(70)90120-7. [DOI] [PubMed] [Google Scholar]
  23. Ligtenberg M. J., Bitter W., Kieft R., Steverding D., Janssen H., Calafat J., Borst P. Reconstitution of a surface transferrin binding complex in insect form Trypanosoma brucei. EMBO J. 1994 Jun 1;13(11):2565–2573. doi: 10.1002/j.1460-2075.1994.tb06546.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. Means G. E., Feeney R. E. Reductive alkylation of amino groups in proteins. Biochemistry. 1968 Jun;7(6):2192–2201. doi: 10.1021/bi00846a023. [DOI] [PubMed] [Google Scholar]
  25. Octave J. N., Schneider Y. J., Crichton R. R., Trouet A. Transferrin uptake by cultured rat embryo fibroblasts. The influence of temperature and incubation time, subcellular distribution and short-term kinetic studies. Eur J Biochem. 1981 Apr;115(3):611–618. [PubMed] [Google Scholar]
  26. Overath P., Chaudhri M., Steverding D., Ziegelbauer K. Invariant surface proteins in bloodstream forms of Trypanosoma brucei. Parasitol Today. 1994 Feb;10(2):53–58. doi: 10.1016/0169-4758(94)90393-x. [DOI] [PubMed] [Google Scholar]
  27. Pays E., Tebabi P., Pays A., Coquelet H., Revelard P., Salmon D., Steinert M. The genes and transcripts of an antigen gene expression site from T. brucei. Cell. 1989 Jun 2;57(5):835–845. doi: 10.1016/0092-8674(89)90798-8. [DOI] [PubMed] [Google Scholar]
  28. RODRIGUEZ J., DEINHARDT F. Preparation of a semipermanent mounting medium for fluorescent antibody studies. Virology. 1960 Oct;12:316–317. doi: 10.1016/0042-6822(60)90205-1. [DOI] [PubMed] [Google Scholar]
  29. Rudolph J. R., Regoeczi E. Isolation of the rat transferrin receptor by affinity chromatography. J Chromatogr. 1987 Jun 19;396:369–373. doi: 10.1016/s0021-9673(01)94076-2. [DOI] [PubMed] [Google Scholar]
  30. Schell D., Borowy N. K., Overath P. Transferrin is a growth factor for the bloodstream form of Trypanosoma brucei. Parasitol Res. 1991;77(7):558–560. doi: 10.1007/BF00931012. [DOI] [PubMed] [Google Scholar]
  31. Schell D., Evers R., Preis D., Ziegelbauer K., Kiefer H., Lottspeich F., Cornelissen A. W., Overath P. A transferrin-binding protein of Trypanosoma brucei is encoded by one of the genes in the variant surface glycoprotein gene expression site. EMBO J. 1991 May;10(5):1061–1066. doi: 10.1002/j.1460-2075.1991.tb08045.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. Steverding D., Stierhof Y. D., Chaudhri M., Ligtenberg M., Schell D., Beck-Sickinger A. G., Overath P. ESAG 6 and 7 products of Trypanosoma brucei form a transferrin binding protein complex. Eur J Cell Biol. 1994 Jun;64(1):78–87. [PubMed] [Google Scholar]
  33. Stieger J., Wyler T., Seebeck T. Partial purification and characterization of microtubular protein from Trypanosoma brucei. J Biol Chem. 1984 Apr 10;259(7):4596–4602. [PubMed] [Google Scholar]
  34. Trowbridge I. S., Collawn J. F., Hopkins C. R. Signal-dependent membrane protein trafficking in the endocytic pathway. Annu Rev Cell Biol. 1993;9:129–161. doi: 10.1146/annurev.cb.09.110193.001021. [DOI] [PubMed] [Google Scholar]
  35. Turkewitz A. P., Amatruda J. F., Borhani D., Harrison S. C., Schwartz A. L. A high yield purification of the human transferrin receptor and properties of its major extracellular fragment. J Biol Chem. 1988 Jun 15;263(17):8318–8325. [PubMed] [Google Scholar]
  36. Van Meirvenne N., Janssens P. G., Magnus E. Antigenic variation in syringe passaged populations of Trypanosoma (Trypanozoon) brucei. 1. Rationalization of the experimental approach. Ann Soc Belg Med Trop. 1975;55(1):1–23. [PubMed] [Google Scholar]
  37. Webster P. Endocytosis by African trypanosomes. I. Three-dimensional structure of the endocytic organelles in Trypanosoma brucei and T. congolense. Eur J Cell Biol. 1989 Aug;49(2):295–302. [PubMed] [Google Scholar]
  38. Webster P., Grab D. J. Intracellular colocalization of variant surface glycoprotein and transferrin-gold in Trypanosoma brucei. J Cell Biol. 1988 Feb;106(2):279–288. doi: 10.1083/jcb.106.2.279. [DOI] [PMC free article] [PubMed] [Google Scholar]
  39. Webster P., Russell D. G. The flagellar pocket of trypanosomatids. Parasitol Today. 1993 Jun;9(6):201–206. doi: 10.1016/0169-4758(93)90008-4. [DOI] [PubMed] [Google Scholar]
  40. Zomerdijk J. C., Kieft R., Duyndam M., Shiels P. G., Borst P. Antigenic variation in Trypanosoma brucei: a telomeric expression site for variant-specific surface glycoprotein genes with novel features. Nucleic Acids Res. 1991 Apr 11;19(7):1359–1368. doi: 10.1093/nar/19.7.1359. [DOI] [PMC free article] [PubMed] [Google Scholar]
  41. van Driel I. R., Stearne P. A., Grego B., Simpson R. J., Goding J. W. The receptor for transferrin on murine myeloma cells: one-step purification based on its physiology, and partial amino acid sequence. J Immunol. 1984 Dec;133(6):3220–3224. [PubMed] [Google Scholar]

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