The Immunoprotein Scolexin and Its Synthesizing Sites — The Midgut Epithelium and the Epidermis


Scolexin is one of the bacterial induced hemolymph proteins of tobacco hornworm (Manduca sexta) larvae, that has hemocyte coagulation-provoking activity. The 72 kDa scolexin complex is composed of two 36 kDa subunits. To examine the protein secretory pathways in insect epithelia a polyclonal antibody was raised against the 36 kDa hemolymph protein. This MsH36 antibody recognised a 36 and a 72 kDa protein in tissue homogenates. On the basis of the characteristic labelling pattern observed on immunoblots and immunocytochemical sections we concluded that the 36 kDa protein in the hemolymph, in the midgut and in the epidermis was identical with the scolexin subunit. In present paper we report a labelling shift in the midgut epithelium between goblet and columnar cells that may be controlled by the hormonal system. A 72 kDa protein showed similar epitops and molecular weight to the scolexin complex and was detected in epidermis and in cuticle under both reducing and non-reducing conditions. Tissue localization of 36 kDa and 72 kDa MsH36 antibody labelling proteins indicated the possibility that the epidermal cells produce two kinds of scolexin-like proteins. The complex composed of 36 kDa subunits are transported basolaterally into the circulation and display hemocyte coagulation inducing activity while the 72 kDa form contains two subunits linked covalently secreted apically into the cuticle.


  1. 1.

    Aronson, A. I., Geng, C., Wu, L. (1999) Aggregation of bacillus thuringiensis Cry1A toxins upon binding to target insect larval midgut vesicles. Appl. Environ. Microbiol. 65, 2503–2507.

    CAS  PubMed Central  Google Scholar 

  2. 2.

    Borhegyi, H. N., Molnár, K., Csikös, Gy., Sass, M. (1999) Isolation and characterisation of an apically sorted 41 kDa protein from the midgut of tobacco hornworm (Manduca sexta). Cell Tissue Res. 297, 513–525.

    CAS  Article  Google Scholar 

  3. 3.

    Cioffi, M. (1979) The morphology and fine structure of the larval mindgut of a moth (Manduca sexta) in relation to active ion transport. Tissue Cell 11, 467–479.

    CAS  Article  Google Scholar 

  4. 4.

    Csikós, Gy, Molnár, K., Borhegyi, H. N., Talián, Cs. G., Sass, M. (1999) Insect cuticle, an in vivo model of protein trafficking. J. Cell Sci. 112, 2113–2124.

    PubMed  Google Scholar 

  5. 5.

    Finnerty, C. M., Granados, R. R. (1997) The plasma protein scolexin from Manduca sexta is induced by baculovirus infection and other immune challenges. Insect Biochem. Mol. Biol. 27, 1–7.

    CAS  Article  Google Scholar 

  6. 6.

    Finnerty, C. M., Granados, R. R., Hughes, P. R., Belotti, A. C. (1994) Bioassay of several baculoviruses for virus induced mortality in Manduca sexta larvae and induction of infection-specific protein. J. Invert. Path. 63, 140–144.

    Article  Google Scholar 

  7. 7.

    Finnerty, C. M., Karplus, P. A., Granados, R. R. (1999) The insect immune protein scolexin is a novel serine proteinase homolog. Protein Science 8, 242–248.

    CAS  Article  Google Scholar 

  8. 8.

    Hua, G., Tsukamoto, K., Rasilo, M. L., Ikezawa, H. (1999) Molecular cloning of a GPI-anchored aminopeptidase N from Bombyx mori midgut: a putative receptor for Bacillus thuringiensis CryIA toxin. Gene 214, 177–185.

    Article  Google Scholar 

  9. 9.

    Hughes, J. A., Hurlbert, R. E., Rupp, R. A., Spence, K. D. (1983) Bacteria-induced haemolymph proteins of Manduca sexta pupae and larvae. J. Insect. Physiol. 29, 625–632.

    CAS  Article  Google Scholar 

  10. 10.

    Hurlbert, R. E., Karlinsey, J. E., Spence, K. D. (1985) Differential synthesis of bacteria-induced proteins of Manduca sexta larvae and pupae. J. Insect. Physiol. 31, 205–215.

    CAS  Article  Google Scholar 

  11. 11.

    Kyriakides, T. R., McKillip, J. L., Spence, K. D. (1995) Biochemical characterization, developmental expression, and induction of the immune protein scolexin from Manduca sexta. Arch. Insect Biochem. Physiol. 29, 269–280.

    CAS  Article  Google Scholar 

  12. 12.

    Laemmli, U. K. (1970) Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature 227, 680–685.

    CAS  Article  Google Scholar 

  13. 13.

    Locke, M., Kiss, A., Sass, M. (1994) The cuticular localization of integument peptides from particular routing categories. Tissue Cell 26, 707–734.

    CAS  Article  Google Scholar 

  14. 14.

    Marcu, O., Locke, M. (1999) The origin, transport and cleavage of the moult-associated cuticular protein CECP22 from Calpodes ethlius (Lepidoptera, Hesperidae). J. Insect Physiol. 45, 861–870.

    CAS  Article  Google Scholar 

  15. 15.

    Minnick, M. F., Rupp, R. A., Spence, K. D. (1986) A bacterial-induced lectin which triggers hemocyte coagulation in Manduca sexta. Biochem. Biophys. Res. Comm. 137, 729–735.

    CAS  Article  Google Scholar 

  16. 16.

    Minnick, M. F., Spence, K. D. (1988) Tissue site and modification of a bacteria induced coagulation protein in Manduca sexta. Insect Biochem. 18, 637–644.

    CAS  Article  Google Scholar 

  17. 17.

    Palli, S. R., Locke, M. (1987) The synthesis of hemolymph proteins by the larval midgut of an insect Calpodes ethlius (Lepidoptera: Hesperidae). Insect Biochem. 17, 561–572.

    CAS  Article  Google Scholar 

  18. 18.

    Russell, V. W., Dunn, P. E. (1991) Lysosyme in the midgut of Manduca sexta during metamorphosis. Arch. Insect Biochem. Physiol. 17, 67–80

    CAS  Article  Google Scholar 

  19. 19.

    Samuels, R. I., Reynolds, S. E. (1993) Moulting fluid enzymes of the tobacco hornworm, Manduca sexta: timing of proteolytic and chinolytic activity in relation to pre-ecdysial development. Arch. Insect Biochem. Physiol. 24, 33–44.

    CAS  Article  Google Scholar 

  20. 20.

    Sass, M., Kiss, A., Locke, M. (1993) Classes of integument peptides. Insect Biochem. Mol. Biol. 23, 845–857.

    CAS  Article  Google Scholar 

  21. 21.

    Towbin, H., Staehelin, T., Gordon, J. (1979) Electroforetic transfer of proteins from polyacrylamide gels to nitrocellulose sheets: procedure and some application. Nat. Acad. Sci. USA 76, 4350–4354.

    CAS  Article  Google Scholar 

  22. 22.

    Willott, E., Trenczek, T., Thrower, L.W., Kanost, M. R. (1994) Immunochemical identification of insect hemocyte populations: monoclonal antibodies distinguish four major hemocyte types in Manduca sexta. Eur. J. Cell. Biol. 65, 417–423.

    CAS  PubMed  Google Scholar 

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Correspondence to Kinga Molnár.

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Dedicated to Professor János Kovács on the occasion of his 70th birthday.

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Molnár, K., Borhegyi, N.H., Csikós, G. et al. The Immunoprotein Scolexin and Its Synthesizing Sites — The Midgut Epithelium and the Epidermis. BIOLOGIA FUTURA 52, 473–484 (2001).

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  • Scolexin
  • secretory pathway
  • midgut
  • epidermis
  • cuticle