Springer Nature is making SARS-CoV-2 and COVID-19 research free. View research | View latest news | Sign up for updates

Transport of phosphatidylcholine toXenopus photoreceptor rod outer segments in the presence of tunicamycin

  • 33 Accesses

  • 4 Citations


Study of the dynamics of membrane protein and phospholipid transport from the inner to the outer segment of vertebrate photoreceptors has shown an interesting dissociation of the two components under a number of experimental treatments which inhibit protein synthesis or transport. Under conditions which block the addition of opsin to outer segments, various lipids continue to be synthesized and transported to the outer segment in the presence of monensin, puromycin, brefeldin A, tunicamycin and several general metabolic inhibitors. In the current study, isolated retinas from adultXenopus laevis were incubated with or without 20 μg mg−1 of tunicamycin in total darkness or light for 2–12 h in the presence of [3H]choline to study the dependence of phosphatidylcholine synthesis and transport on protein transport to the outer segment. Phosphatidylcholine is a major bulk lipid of outer segments, comprising close to one half of the phospholipid of outer segment phospholipids, and blocking choline uptake in retinas is known to cause photoreceptor degeneration. Biochemical analysis demonstrates that tunicamycin does not block the synthesis of phosphatidylcholine in photoreceptor inner segments or transport of radiolabelled phosphatidylcholine to outer segments during 6 h incubations with [3H]choline in light or total darkness. Light and electron microscopic autoradiography and morphometric analysis show that [3H]choline radiolabelled phospholipid does not accumulate in a band of newly formed basal discs in the outer segment or in the tubulo-vesicular structures which accumulate in the intersegmental space of tunicamycin-treated retinas. We conclude that transport of phosphatidylcholine can occur independently of opsin transport to the outer segment but whether this represents two separable components of a single pathway or involves two distinct routes of transport to the outer segment is still unresolved.

This is a preview of subscription content, log in to check access.


  1. Anderson, R. E., Feldman, L. S. &Feldman, G. L. (1970) Lipids of ocular tissues. II. The phospholipids of mature bovine and rabbit whole retina.Biochimica et Biophysica Acta 202, 367–73.

  2. Anderson, R. E., Kelleher, P. A. &Maude, M. B. (1980a) Metabolism of phosphatidyl-ethanolamine in the frog retina.Biochimica et Biophysica Acta 620, 227–35.

  3. Anderson, R. E., Kelleher, P. A., Maude, M. B. &Maida, T. M. (1980b) Synthesis and turnover of lipid and protein components of frog retinal rod outer segments.Neurochemistry 1, 29–42.

  4. Anderson, R. E., Maude, M. B., Pu, G. A.-W. &Hollyfield, J. G. (1985) Effect of light on the metabolism of lipids in the rat retina.Journal of Neurochemistry 44, 773–8.

  5. Anderson, R. E., Maude, M. B., Kelleher, P. A., Maida, T. M. &Basinger, S. F. (1980c) Metabolism of phosphatidylcholine in the frog retina.Biochimica et Biophysica Acta 620, 212–26.

  6. Basinger, S. &Hoffman, R. (1976) Phosphatidyl choline metabolism in the frog rod photoreceptor.Experimental Eye Research 23, 117–26.

  7. Besharse, J. C. (1986) Photosensitive membrane turnover: differentiated membrane domains and cell-cell interaction. In:The Retina: A Model for Cell Biological Studies.Part I (edited byAdler, R. &Farber, D.) pp. 297–352. New York: Academic Press.

  8. Besharse, J. C. &Dunis, D. A. (1983) Rod photoreceptor disc shedding in eye cups: relationship to bicarbonate and amino acids.Experimental Eye Research 36, 567–80.

  9. Besharse, J. C. &Horst, C. J. (1990) The photoreceptor connecting cilium: a model for the transition zone. In:The Structure and Function of Ciliary and Flagellar Membrane Surfaces (edited byBloodgood, R. A.) pp. 389–417. New York: Plenum Press.

  10. Besharse, J. C., Forestner, D. M. &Defoe, D. M. (1985) Membrane assembly in retinal photoreceptors. III. Distinct membrane domains of the connecting cilium of developing rods.Journal of Neuroscience 5, 1035–48.

  11. Besharse, J. C., Hollyfield, J. G. &Rayborn, M. E. (1977) Turnover of rod photoreceptor outer segments. II. Membrane addition and loss in relationship to light.Journal of Cell Biology 75, 507–27.

  12. Bibb, C. &Young, R. W. (1974a) Renewal of fatty acids in the membranes of visual cell outer segments.Journal of Cell Biology 61, 327–43.

  13. Bibb, C. &Young, R. W. (1974b) Renewal of glycerol in the visual cells and pigment epithelium of the frog retina.Journal of Cell Biology 62, 378–89.

  14. Bok, D. &Young, R. W. (1972) The renewal of diffusely distributed proteins in the outer segments of rods and cones.Vision Research 12, 161–8.

  15. Deretic, D. &Papermaster, D. S. (1991) Polarized sorting of rhodopsin on post-Golgi membranes in frog retinal photoreceptor cells.Journal of Cell Biology 113, 1281–93.

  16. Dudley, P. A., Alligood, J. P. &O'Brien, P. J. (1984) Biochemical events related to circadian photoreceptor shedding. In:Molecular and Cellular Basis of Visual Acuity, Cell and Developmental Biology of the Eye (edited byHilfer, S. R. &Sheffield, J. B.) pp. 13–30. New York: Springer-Verlag.

  17. Dudley, P. A. &Anderson, R. E. (1978) Phospholipid transfer protein from bovine retina with high activity towards retinal rod disc membranes.FEBS Letters 95, 57–60.

  18. Fliesler, S. J. &Anderson, R. E. (1983) Chemistry and metabolism of lipids in the vertebrate retina.Progress in Lipid Research 22, 79–131.

  19. Fliesler, S. J. &Basinger, S. F. (1985) Tunicamycin blocks the incorporation of opsin into retinal rod outer segment membranes.Proceedings of the National Academy of Sciences (USA) 82, 1116–20.

  20. Fliesler, S. J. &Basinger, S. F. (1987) Monensin stimulates glycerolipid incorporation into rod outer segment membranes.Journal of Biological Chemistry 262, 17516–23.

  21. Fliesler, S. J., Rapp, L. M. &Hollyfield, J. G. (1984) Photoreceptor-specific degeneration caused by tunicamycin.Nature 311, 575–7.

  22. Fliesler, S. J., Rayborn, M. E. &Hollyfield, J. G. (1985) Membrane morphogenesis in retinal rod outer segments: inhibition by tunicamycin.Journal of Cell Biology 100, 574–87.

  23. Fliesler, S. J., Rayborn, M. E. &Hollyfield, J. G. (1986) Inhibition of oligosaccharide processing and membrane morphogenesis in retinal rod photoreceptor cells.Proceedings of the National Academy of Sciences (USA) 83, 6435–9.

  24. Folch, J., Lees, M. &Sloane Stanley, G. H. (1957) A simple method for the isolation and purification of total lipides from animal tissues.Journal of Biological Chemistry 226, 497–509.

  25. Gordon, W. C. &Bazan, N. G. (1990) Docosahexaenoic acid utilization during rod photoreceptor cell renewal.Journal of Neuroscience 10, 2190–202.

  26. Hall, M. O., Basinger, S. F. &Bok, D. (1973) Studies on the assembly of rod outer segment disc membranes. In:Biochemistry and Physiology of the Visual Pigments (edited byLanger, H.) pp. 319–26. New York: Springer-Verlag.

  27. Hicks, D. &Barnstable, C. J. (1986) Lectin and antibody labelling of developing rat photoreceptor cells: an electron microscope immunocytochemical study.Journal of Neurocytology 15, 219–30.

  28. Hollyfield, J. G., Rayborn, M. E., Verner, G. E., Maude, M. B. &Anderson, R. E. (1982) Membrane addition to rod photoreceptor outer segments: light stimulates membrane assembly in the absence of increased membrane biosynthesis.Investigative Ophthalmology and Visual Science 22, 417–27.

  29. Horst, C. J., Forestner, D. M. &Besharse, J. C. (1987) Cytoskeletal-membrane interactions. A stable interaction between cell surface glycoconjugates and doublet microtubules of the photoreceptor connecting cilium.Journal of Cell Biology 105, 2973–87.

  30. Keller, R. K. &Fliesler, S. J. (1989) Newly synthesized isoprenoids and opsin are transported via independent pathways to the rod outer segment (ROS).Investigative Ophthalmology and Visual Science 30, 286 (Abstract).

  31. Keller, R. K. &Fliesler, S. J. (1990) Brefeldin A blocks transport of proteins, but not lipids, to the rod outer segment.Investigative Ophthalmology and Visual Science 31, 470 (Abstract).

  32. Keller, R. K. &Fliesler, S. J. (1991) Intracellular transport of phospholipids, squalene, and protein to the rod outer segment is differentially affected by temperature and energy inhibitors.Investigative Ophthalmology and Visual Science 32, 1009 (Abstract).

  33. Lettre, H. &Paweletz, N. (1966) Probleme der elektronmikroskopischen autoradiographie.Naturwissenschaften 53, 268–71.

  34. Li, J., Gentleman, S., Wetzel, M. G., O'Brien, P. &Chader, G. J. (1992) Studies on the docosahexaenoic acid binding proteins in retina cytosol.Investigative Ophthalmology and Visual Sciences 33, 1189 (Abstract).

  35. Masland, R. H. &Mills, J. W. (1979) Autoradiographic identification of acetylcholine in the rabbit retina.Journal of Cell Biology 83, 159–78.

  36. Masland, R. &Mills, J. W. (1980) Choline accumulation by photoreceptor cells of the rabbit retina.Proceedings of the National Academy of Sciences (USA)77, 1671–5.

  37. Matheke, M. L. &Holtzman, E. (1984) The effects of monensin and of puromycin on transport of membrane components in the frog retinal photoreceptor. II. Electron microscopic autoradiography of proteins and glycerolipids.Journal of Neuroscience 4, 1093–103.

  38. Matheke, M. L., Fliesler, S. J., Basinger, S. F. &Holtzman, E. (1984) The effects of monensin on transport of membrane components in the frog retinal photoreceptor. I. Light microscope autoradiography and biochemical analysis.Journal of Neuroscience 4, 1086–92.

  39. Mercurio, A. M. &Holtzman, E. (1982) Ultrastructural localization of glycerolipid synthesis in rod cells of the isolated frog retina.Journal of Neurocytology 11, 295–322.

  40. Muresan, V. &Besharse, J. C. (1991) Complex intermolecular interactions maintain a stable linkage between the photoreceptor connecting cilium axoneme and plasma membrane.Journal of Cell Biology 115, 165a (Abstract).

  41. Muresan, V. &Besharse, J. C. (1993) Plasmalemmal glycoproteins in the photoreceptor connecting cilium associate with the axoneme via stable but distinctive interactions.Investigative Ophthalmology and Visual Science 34, 1200 (Abstract).

  42. Muresan, V. &Besharse, J. C. (1994) Complex intermolecular interactions maintain a stable linkage between the photoreceptor connecting cilium axoneme and plasma membrane.Cell Motility and the Cytoskeleton (in press).

  43. Nir, I., Cohen, D. &Papermaster, D. S. (1984) Immunological localization of opsin in the cell membrane of dystrophic RCS rats.Journal of Cell Biology 98, 1788–95.

  44. Osborne, M. P. &Monaghan, P. (1976) Differential sensitivity of rods and cones inXenopus retina to hemicholinium-3.Cell and Tissue Research 175, 59–72.

  45. Plantner, J. J., Poncz, L. &Kean, E. L. (1980) Effect of tunicamycin on glycosylation of rhodopsin.Archives of Biochemistry and Biophysics 201, 527–32.

  46. Pu, G. A.-W. &Anderson, R. E. (1983) Alteration of retinal choline metabolism in an experimental model for photoreceptor cell degeneration.Investigative Ophthalmology and Visual Science 24, 288–93.

  47. Pu, G. A.-W. &Masland, R. H. (1984) Biochemical interruption of membrane phospholipid renewal in retinal photoreceptor cells.Journal of Neuroscience 4, 1559–76.

  48. Richardson, T. M. (1969) Cytoplasmic and ciliary connections between the inner and outer segments of mammalian visual receptors.Vision Research 9, 727–31.

  49. Rohlich, P. (1975) The sensory cilium of retinal rods is analogous to the transitional zone of motile cilia.Cell and Tissue Research 161, 421–30.

  50. Rouser, G., Fleischer, S. &Yamamoto, A. (1970) Two dimensional thin-layer chromatographic separation of polar lipids and determination of phospholipids by phosphorus analysis of spots.Lipids 5, 494–6.

  51. Swartz, J. G. &Mitchell, J. E. (1970) Biosynthesis of retinal phospholipids: incorporation of radioactivity from labeled phosphorylcholine and cytidine diphosphate choline.Journal of Lipid Research 11, 544–50.

  52. Trump, B. F. &Bulger, R. E. (1966) New ultrastructural characteristics of cells fixed in a glutaraldehyde-osmium tetroxide mixture.Laboratory Investigation 15, 368–79.

  53. Wetzel, M. G. &Besharse, J. C. (1991) Ultrastructural analysis of the intersegmental space ofXenopus rod photoreceptors during periods of active disc assembly.Investigative Ophthalmology and Visual Science 32, 846 (Abstract).

  54. Wetzel, M. G. &O'Brien, P. J. (1986) Turnover of palmitate, arachidonate and glycerol in phospholipids of rat rod outer segments.Experimental Eye Research 43, 941–54.

  55. Wetzel, M. G., Bendala-Tufanisco, E. &Besharse, J. C. (1993) Tunicamycin does not inhibit transport of phosphatidylinositol toXenopus rod outer segments.Journal of Neurocytology 22, 397–412.

  56. Williams, M. A. (1977) In:Practical Methods in Electron Microscopy: Autoradiography and Immunocytochemistry (edited byGlauert, A. M.) pp. 110–17. New York: North Holland Publishing Company.

  57. Young, R. W. (1967) The renewal of photoreceptor cell outer segments.Journal of Cell Biology 33, 61–72.

  58. Young, R. W. &Droz, B. (1968) The renewal of proteins in retinal rods and cones.Journal of Cell Biology 39, 169–84.

Download references

Author information

Correspondence to M. G. Wetzel.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Wetzel, M.G., Besharse, J.C. Transport of phosphatidylcholine toXenopus photoreceptor rod outer segments in the presence of tunicamycin. J Neurocytol 23, 333–342 (1994). https://doi.org/10.1007/BF01666523

Download citation


  • Phosphatidylcholine
  • Outer Segment
  • Monensin
  • Tunicamycin
  • Total Darkness