Skip to main content Accessibility help
  • Get access
    Check if you have access via personal or institutional login
  • Cited by 6
  • Print publication year: 2005
  • Online publication date: August 2009

3 - Novel Pathways of Protein Secretion



Intercellular communications are fundamental for many of the biological processes that are involved in the survival of living organisms, and secretory proteins are among the most important messengers in this network of information. Proteins destined for this function are endowed with a hydrophobic signal peptide which targets them to the endoplasmic reticulum (ER) and are released in the extracellular environment by a ‘classical’ pathway of constitutive or regulated secretion. However, in the early 1990s it became evident that non-classical mechanisms must exist for the secretion of some proteins which, despite their extracellular localisation and function, lack a signal peptide. Indeed, the family of these leaderless secretory proteins continues to grow and comprises proteins that, although apparently unrelated, share both structural and functional features. This chapter will review current hypotheses on the mechanisms underlying non-classical secretion and discuss their implications in the regulation of the inflammatory and immune response. The relevance of non-classical secretion pathways to molecular chaperone biology is also discussed in Chapters 2 and 12.

Leaderless secretory proteins

Secretory mechanisms that are discrete to the classical pathways appear early in evolution. Gram negative bacteria are endowed with many (up to six) types of secretion mechanisms that are, at least in part, independent of the general secretory pathway, the prototype being the haemolysin secretion system [1]. In addition, two pathways of secretion that avoid the ER exist in yeast.

de Lima Pimenta A, Blight M A, Chervaux C and Holland I B. Protein secretion in Gram negative bacteria. In Kuchler, K., Rubartelli, A. and Holland, B. (Eds.) Unusual Secretory Pathways: From Bacteria to Man. Chapman & Hall Landes Bioscience, New York/Austin, TX 1997, pp 1–48
Cleves, A E, Cooper, D N, Barondes, S H and Kelly, R B. A new pathway for protein export in Saccharomyces cerevisiae. J Cell Biol 1996, 133: 1017–1026
Kuchler K and Egner R. Unusual protein secretion and translocation pathways in yeast: implication of ABC transporters. In Kuchler, K., Rubartelli, A. and Holland, B. (Eds.) Unusual Secretory Pathways: From Bacteria to Man. Chapman & Hall Landes Bioscience, New York/Austin, TX 1997, pp 49–86
Rubartelli A and Sitia R. Secretion of mammalian proteins that lack a signal sequence. In Kuchler, K., Rubartelli, A. and Holland, B. (Eds.) Unusual Secretory Pathways: From Bacteria to Man. Chapman & Hall Landes Bioscience, New York/Austin, TX 1997, pp 87–115
Rubartelli, A, Cozzolino, F, Talio, M and Sitia, R. A novel secretory pathway for interleukin-1 beta, a protein lacking a signal sequence. EMBO J 1990, 9: 1503–1510
Rubartelli, A, Bajetto, A, Allavena, G, Wollman, E and Sitia, R. Secretion of thioredoxin by normal and neoplastic cells through a leaderless secretory pathway. J Biol Chem 1992, 267: 24161–24164
Dinarello, C A. Proinflammatory cytokines. Chest 2000, 118: 503–508
Werman, A, Werman-Venkent, R, White, R, Lee, J K, Werman, B, Krelin, Y, Voronov, E, Dinarello, C A, and Apte, R N.The precursor form of IL1alpha is an intracrine proinflammatory activator of transcription. Proc Natl Acad Sci U S A, 2004, 101: 2434–2439
Dinarello, C A and Fantuzzi, G. Interleukin-18 and host defense against infection. J Infect Dis 2003, 187: S370–S384
Fantuzzi, G and Dinarello, C A. Interleukin-18 and interleukin-1 β: two cytokine substrates for ICE (caspase-1). J Clin Immunol 1999, 19: 1–11
Laliberte, R E, Eggler, J and Gabel, C A. ATP treatment of human monocytes promotes caspase-1 maturation and externalization. J Biol Chem 1999, 274: 36944–36951
Cruikshank, W W, Kornfeld, H and Center, D M. Interleukin-16. J Leuk Biol 2000, 67: 757–766
Christofori G. The role of fibroblast growth factors in tumour progression and angiogenesis. In Bicknell, R., Lewis, C. E. and Ferrara, N. (Eds.) Tumour Angiogenesis. Oxford University Press, Oxford, UK 1997, pp 201–238
Bikfalvi, A, Savona, C, Perollet, C and Javerzat, S. New insights in the biology of fibroblast growth factor-2. Angiogenesis 1998, 1: 155–173
Tsai, S J, Wu, M H, Chen, H M, Chuang, P C and Wing, L Y. Fibroblast growth factor-9 is an endometrial stromal growth factor. Endocrinology 2002, 143: 2715–2721
Sleeman, M W, Anderson, K D, Lambert, P D, Yancopoulos, G D and Wiegand, S J. The ciliary neurotrophic factor and its receptor, CNTFR alpha. Pharm Acta Helv 2000, 74: 265–272
Calandra, T. Macrophage migration inhibitory factor and host innate immune responses to microbes. Scand J Infect Dis 2003, 35: 573–576
Ko, Y G, Park, H, Kim, T, Lee, J W, Park, S G, Seol, W, Kim, J E, Lee, W H, Kim, S H, Park, J E and Kim, S. A cofactor of tRNA synthetase, p43, is secreted to up-regulate proinflammatory genes. J Biol Chem 2001, 276: 23028–23033
Berger, A C, Alexander, H R, Tang, G, Wu, P S, Hewitt, S M, Turner, E, Kruger, E, Figg, W D, Grove, A, Kohn, E, Stern, D and Libutti, S K. Endothelial monocyte activating polypeptide II induces endothelial cell apoptosis and may inhibit tumor angiogenesis. Microvasc Res 2000, 60: 70–80
Rescher, U, Zobiack, N and Gerke, V. Intact Ca2+-binding sites are required for targeting of annexin 1 to endosomal membranes in living HeLa cells. J Cell Sci 2000, 113: 3931–3938
Solito, E, Nuti, S and Parente, L. Dexamethasone-induced translocation of lipocortin (annexin) 1 to the cell membrane of U-937 cells. Br J Pharmacol 1994, 112: 347–348
Christmas, P, Callaway, J, Fallon, J, Jones, J and Haigler, H T. Selective secretion of annexin 1, a protein without a signal sequence, by the human prostate gland. J Biol Chem 1991, 266: 2499–2507
Tsutsumi, S, Yanagawa, T, Shimura, T, Fukumori, T, Hogan, V, Kuwano, H and Raz, A. Regulation of cell proliferation by autocrine motility factor/phosphoglucose isomerase signaling. J Biol Chem 2003, 278: 32165–32172
Arner, E S and Holmgren, A. Physiological functions of thioredoxin and thioredoxin reductase. Eur J Biochem 2000, 267: 6102–6109
Rabinovich, G A, Baum, L G, Tinari, N, Paganelli, R, Natoli, C, Liu, F T and Iacobelli, S. Galectins and their ligands: amplifiers, silencers or tuners of the inflammatory response?Trends Immunol 2002, 23: 313–320
Rabinovich, G A, Rubinstein, N and Toscano, M A. Role of galectins in inflammatory and immunomodulatory processes. Biochim Biophys Acta 2002, 1572: 274–284
Sano, H, Hsu, D K, Apgar, J R, Yu, L, Sharma, B B, Kuwabara, I, Izui, S and Liu, F T. Critical role of galectin-3 in phagocytosis by macrophages. J Clin Invest 2003, 112: 389–397
Griffin, M, Casadio, R and Bergamini, C M. Transglutaminases: Nature's biological glues. Biochem J 2002, 368: 377–396
Grundmann, U, Amann, E, Zettlmeissl, G and Kupper, H A. Characterization of cDNA coding for human factor XIIIa. Proc Natl Acad Sci USA 1986, 83: 8024–8028
Wang, H, Bloom, O, Zhang, M, Vishnubhakat, J M, Ombrellino, M, Che, J, Frazier, A, Yang, H, Ivanova, S, Borovikova, L, Manogue, K R, Faist, E, Abraham, E, Andersson, J, Andersson, U, Molina, P E, Abumrad, N N, Sama, A and Tracey, K J. HMG-1 as a late mediator of endotoxin lethality in mice. Science 1999, 285: 248–251
Maizel, A, Tassetto, M, Filhol, O, Cochet, C, Prochiantz, A and Joliot, A. Engrailed homeoprotein secretion is a regulated process. Development 2002, 129: 3545–3553
Maizel, A, Bensaude, O, Prochiantz, A and Joliot, A. A short region of its homeodomain is necessary for engrailed nuclear export and secretion. Development 1999, 126: 3183–3190
Dagher, S F, Wang, J L and Patterson, R J. Identification of galectin-3 as a factor in pre-mRNA splicing. Proc Natl Acad Sci USA 1995, 92: 1213–1217
Kleemann, R, Hausser, A, Geiger, G, Mischke, R, Burger-Kentischer, A, Flieger, O, Johannes, F J, Roger, T, Calandra, T, Kapurniotu, A, Grell, M, Finkelmeier, D, Brunner, H and Bernhagen, J. Intracellular action of the cytokine MIF to modulate AP-1 activity and the cell cycle through Jab1. Nature 2000, 408: 211–216
Vareli, K, Frangou-Lazaridis, M, Kraan, I, Tsolas, O and Driel, R. Nuclear distribution of prothymosin alpha and parathymosin: evidence that prothymosin alpha is associated with RNA synthesis processing and parathymosin with early DNA replication. Exp Cell Res 2000, 257: 152–161
Hannappel, E and Huff, T. The thymosins. Prothymosin alpha, parathymosin, and beta-thymosins: structure and function. Vit Horm 2003, 66: 257–296
Focher, F and Spadari, S. Thymidine phosphorylase: a two-face Janus in anticancer chemotherapy. Cur Cancer Drug Targets 2001, 1: 141–153
Jackson, A, Tarantini, F, Gamble, S, Friedman, S and Maciag, T. The release of fibroblast growth factor-1 from NIH 3T3 cells in response to temperature involves the function of cysteine residues. J Biol Chem 1995, 270: 33–36
Tarantini, F, Gamble, S, Jackson, A and Maciag, T. The cysteine residue responsible for the release of fibroblast growth factor-1 residues in a domain independent of the domain for phosphatidylserine binding. J Biol Chem 1995, 270: 29039–29042
Balklava, Z, Verderio, E, Collighan, R, Gross, S, Adams, J and Griffin, M. Analysis of tissue transglutaminase function in the migration of Swiss 3T3 fibroblasts: the active-state conformation of the enzyme does not affect cell motility but is important for its secretion. J Biol Chem 2002, 277: 16567–16575
Reiness, C G, Seppa, M J, Dion, D M, Sweeney, S, Foster, D N and Nishi, R. Chick ciliary neurotrophic factor is secreted via a nonclassical pathway. Mol Cell Neurosci 2001, 17: 931–944
Menon, R P and Hughes, R C. Determinants in the N-terminal domains of galectin-3 for secretion by a novel pathway circumventing the endoplasmic reticulum-Golgi complex. Eur J Biochem 1999, 264: 569–576
Gong, H C, Honjo, Y, Nangia-Makker, P, Hogan, V, Mazurak, N, Bresalier, R S and Raz, A. The NH2 terminus of galectin-3 governs cellular compartmentalization and functions in cancer cells. Cancer Res 1999, 59: 6239–6245
Bonaldi, T, Talamo, F, Scaffidi, P, Ferrera, D, Porto, A, Bachi, A, Rubartelli, A, Agresti, A and Bianchi, M E. Monocytic cells hyperacetylate chromatin protein HMGB1 to redirect it towards secretion. EMBO J 2003, 22: 5551–5560
Haga, A, Niinaka, Y and Raz, A. Phosphohexose isomerase/autocrine motility factor/neuroleukin/maturation factor is a multifunctional phosphoprotein. Biochim Biophys Acta 2000, 1480: 235–244
Stevenson, F T, Bursten, S L, Fanton, C, Locksley, R M and Lovett, D H. The 31-kDa precursor of interleukin 1 alpha is myristoylated on specific lysines within the 16-kDa N-terminal propiece. Proc Natl Acad Sci USA 1993, 90: 7245–7249
Cooper, D N and Barondes, S H. Evidence for export of a muscle lectin from cytosol to extracellular matrix and for a novel secretory mechanism. J Cell Biol 1990, 110: 1681–1691
Lindstedt, R, Apodaca, G, Barondes, S H, Mostov, K E and Leffler, H. Apical secretion of a cytosolic protein by Madin-Darby canine kidney cells. Evidence for polarized release of an endogenous lectin by a nonclassical secretory pathway. J Biol Chem 1993, 268: 11750–11757
Hermo, L and Jacks, D. Nature's ingenuity: bypassing the classical secretory route via apocrine secretion. Mol Reprod Dev 2002, 63: 394–410
Steinhoff, M, Eicheler, W, Holterhus, P M, Rausch, U, Seitz, J and Aumuller, G. Hormonally induced changes in apocrine secretion of transglutaminase in the rat dorsal prostate and coagulating gland. Eur J Cell Biol 1994, 65: 49–59
Eickhoff, R, Wilhelm, B, Renneberg, H, Wennemuth, G, Bacher, M, Linder, D, Bucala, R, Seitz, J and Meinhardt, A. Purification and characterization of macrophage migration inhibitory factor as a secretory protein from rat epididymis: evidences for alternative release and transfer to spermatozoa. Mol Med 2001, 7: 27–35
MacKenzie, A, Wilson, H L, Kiss-Toth, E, Dower, S K, North, R A and Surprenant, A. Rapid secretion of interleukin-1 β by microvesicle shedding. Immunity 2001, 15: 825–835
Murk, J L, Stoorvogel, W, Kleijmeer, M J and Geuze, H J. The plasticity of multivesicular bodies and the regulation of antigen presentation. Sem Cell Dev Biol 2002, 13: 303–311
Johnstone, R M, Adam, M, Hammond, J R, Orr, L and Turbide, C. Vesicle formation during reticulocyte maturation. Association of plasma membrane activities with released vesicles (exosomes). J Biol Chem 1987, 262: 9412–9420
Théry, C, Zitvogel, L and Amigorena, S. Exosomes: composition, biogenesis and function. Nat Rev Immunol 2002, 2: 569–579
Théry, C, Boussac, M, Véron, P, Ricciardi-Castagnoli, P, Raposo, G, Garin, G and Amigorena, S. Proteomic analysis of dendritic cell-derived exosomes: A secreted subcellular compartment distinct from apoptotic vesicles. J Immunol 2001, 166: 7309–7318
Fink, A L. Chaperone-mediated protein folding. Physiol Rev 1999, 79: 425–449
Holland I B, Benhabdelhak H, Young J, de Lima Pimenta A, Schmitt L and Blight M A. Bacterial ABC transporters involved in protein translocation. In Holland, I. B. (Ed.) ABC Proteins: from Bacteria to Man. Academic Press, London/San Diego 2003, pp 209–242
Prudovsky, I, Bagala, C, Tarantini, F, Mandinova, A, Soldi, R, Bellum, S and Maciag, T. The intracellular translocation of the components of the fibroblast growth factor 1 release complex precedes their assembly prior to export. J Cell Biol 2002, 158: 201–208
McNew, J A and Goodman, J M. An oligomeric protein is imported into peroxisomes in vivo. J Cell Biol 1994, 127: 1245–1257
Cuervo, A M, Mann, L, Bonten, E J, d'Azzo, A and Dice, J F. Cathepsin A regulates chaperone-mediated autophagy through cleavage of the lysosomal receptor. EMBO J 2003, 22: 47–59
Dean, M, Hamon, Y and Chimini, G. The human ATP-binding cassette (ABC) transporter superfamily. J Lipid Res 2001, 42: 1007–1017
Hamon, Y, Luciani, M F, Becq, F, Verrier, B, Rubartelli, A and Chimini, G. Interleukin-1 β secretion is impaired by inhibitors of the ATP binding cassette transporter, ABC1. Blood 1997, 90: 2911–2915
Chapman, L P, Epton, M J, Buckingham, J C, Morris, J F and Christian, H C. Evidence for a role of the adenosine 5′-triphosphate-binding cassette transporter A1 in the externalization of annexin I from pituitary folliculo-stellate cells. Endocrinology 2003, 144: 1062–1073
Flieger, O, Engling, A, Bucala, R, Lue, H, Nickel, W and Bernhagen, J. Regulated secretion of macrophage migration inhibitory factor is mediated by a non-classical pathway involving an ABC transporter. FEBS Lett 2003, 551: 78–86
Schafer, T, Zentgraf, H, Zehe, C, Brugger, B, Bernhagen, J and Nickel, W. Unconventional protein secretion: direct translocation of fibroblast growth factor 2 across the plasma membrane of mammalian cells. J Biol Chem 2003, 279: 6244–6251
Oliani, S M, Damazo, A S and Perretti, M. Annexin 1 localisation in tissue eosinophils as detected by electron microscopy. Med Inflamm 2002, 11: 287–292
Qu, Z, Kayton, R J, Ahmadi, P, Liebler, J M, Powers, M R, Planck, S R and Rosenbaum, J T. Ultrastructural immunolocalization of basic fibroblast growth factor in mast cell secretory granules. Morphological evidence for bfgf release through degranulation. J Histochem Cytochem 1998, 46: 1119–1128
Nishino, T, Bernhagen, J, Shiiki, H, Calandra, T, Dohi, K and Bucala, R. Localization of macrophage migration inhibitory factor (MIF) to secretory granules within the corticotrophic and thyrotrophic cells of the pituitary gland. Mol Med 1995, 1: 781–788
Joliot, A, Maizel, A, Rosenberg, D, Trembleau, A, Dupas, S, Volovitch, M and Prochiantz, A. Identification of a signal sequence necessary for the unconventional secretion of Engrailed homeoprotein. Cur Biol 1998, 8: 856–863
Gardella, S, Andrei, C, Ferrera, D, Lotti, L V, Torrisi, M R, Bianchi, M E and Rubartelli, A. The nuclear protein HMGB1 is secreted by monocytes via a non-classical, vesicle-mediated secretory pathway. EMBO Rep 2002, 3: 995–1001
Andrei, C, Dazzi, C, Lotti, L, Torrisi, M R, Chimini, G and Rubartelli, A. The secretory route of the leaderless protein interleukin 1beta involves exocytosis of endolysosome-related vesicles. Mol Biol Cell 1999, 10: 1463–1475
Gardella, S, Andrei, C, Poggi, A, Zocchi, M R and Rubartelli, A. Control of interleukin-18 secretion by dendritic cells: role of calcium influxes. FEBS Lett 2000, 481: 245–248
Blott, E J and Griffiths, G M. Secretory lysosomes. Nat Rev Mol Cell Biol 2002, 3: 122–131
Sesaki, H, Wong, E F and Siu, C H. The cell adhesion molecule DdCAD-1 in Dictyostelium is targeted to the cell surface by a nonclassical transport pathway involving contractile vacuoles. J Cell Biol 1997, 138: 939–951
Holland, I B.ABC Proteins: from Bacteria to Man. Academic Press, London/San Diego: 2003
Andrei, C, Margiocco, P, Poggi, A, Lotti, L V, Torrisi, M R, Rubartelli, A.Phospholipases C and A2 control lysosome – mediated IL-1beta secretion: Implications for inflammatory processes. Proc Natl Acad Sci USA 2004, 101: 9745–9750
Perregaux, D G, McNiff, P, Laliberte, R, Conklyn, M and Gabel, C A. ATP acts as an agonist to promote stimulus-induced secretion of IL-1 β and IL-18 in human blood. J Immunol 2000, 165: 4615–4623
Di Virgilio, F, Chiozzi, P, Ferrari, D, Falzoni, S, Sanz, J M, Morelli, A, Torboli, M, Bolognesi, G and Baricordi, O R. Nucleotide receptors: an emerging family of regulatory molecules in blood cells. Blood 2001, 97: 587–600
Gardella, S, Andrei, C, Costigliolo, S, Poggi, A, Zocchi, M R and Rubartelli, A. Interleukin-18 synthesis and secretion by dendritic cells are modulated by interaction with antigen-specific T cells. J Leuk Biol 1999, 66: 237–241
Gardella, S, Andrei, C, Lotti, L V, Poggi, A, Torrisi, M R, Zocchi, M R and Rubartelli, A. CD8+ T lymphocytes induce polarized exocytosis of secretory lysosomes by dendritic cells with release of interleukin-1 β and cathepsin D. Blood 2001, 98: 2152–2159
Kamogashira, T, Masui, Y, Ohmoto, Y, Hirato, T, Nagamura, K, Mizuno, K, Hong, Y M, Kikumoto, Y, Nakai, S and Hirai, Y. Site-specific mutagenesis of the human interleukin-1 β gene: structure-function analysis of the cysteine residues. Biochem Biophys Res Comm 1988, 150: 1106–1114
Pei, D S, Fu, Y, Sun, Y F and Zhao, H R. Site-directed mutagenesis of the cysteines of human IL-18 and its effect on IL-18 activity. Sheng Wu Hua Xue Yu Sheng Wu Wu Li Xue Bao (Shanghai) 2002, 34: 57–61
Ortega, S, Schaeffer, M T, Soderman, D, DiSalvo, J, Linemeyer, D L, Gimenez-Gallego, G and Thomas, K A. Conversion of cysteine to serine residues alters the activity, stability, and heparin dependence of acidic fibroblast growth factor. J Biol Chem 1991, 266: 5842–5846
Cho, M and Cummings, R D. Galectin-1, a β -galactoside-binding lectin in Chinese hamster ovary cells. I. Physical and chemical characterization. J Biol Chem 1995, 270: 5198–5206
Kleemann, R, Kapurniotu, A, Mischke, R, Held, J and Bernhagen, J. Characterization of catalytic centre mutants of macrophage migration inhibitory factor (MIF) and comparison to Cys81Ser MIF. Eur J Biochem 1999, 261: 753–766
Angelini, G, Gardella, S, Ardy, M, Ciriolo, M R, Filomeni, G, Di Trapani, G, Clarke, F, Sitia, R and Rubartelli, A. Antigen-presenting dendritic cells provide the reducing extracellular microenvironment required for T lymphocyte activation. Proc Nat Acad Sci USA 2002, 99: 1491–1496
Rogelj, S, Weinberg, R A, Fanning, P and Klagsbrun, M. Basic fibroblast growth factor fused to a signal peptide transforms cells. Nature 1988, 331: 173–175
Sloan, I S, Horowitz, P M and Chirgwin, J M. Rapid secretion by a nonclassical pathway of overexpressed mammalian mitochondrial rhodanese. J Biol Chem 1994, 269: 27625–27630
Tanudji, M, Hevi, S and Chuck, S L. Improperly folded green fluorescent protein is secreted via a non-classical pathway. J Cell Sci 2002, 115: 3849–3857
Lue, H, Kleemann, R, Calandra, T, Roger, T and Bernhagen, J. Macrophage migration inhibitory factor (MIF): mechanisms of action and role in disease. Microbes Infect 2002, 4: 449–460