Exosome-Like Vesicles with Dipeptidyl Peptidase IV in Human Saliva

Abstract

During the last decade, a novel mechanism of protein release has been recognized that involves small (30-100 nm) membrane vesicles termed exosomes. [1][2][3] Exosomal vesicles are secreted following the fusion of multivesicular late endosomes with the plasma membrane. While the range of exosomal proteins depends on cell type, these vesicles commonly carry cell-surface proteins and cytoskeletal proteins. Several physiologic roles have been assigned to exosomes, including the expulsion of obsolete membrane constituents, exchange of cellular material and intercellular communication. Exosome production has been observed in a variety of cell types in vitro, including reticulocytes, 4) cytotoxic T lymphocytes, 5)B lymphocytes, 6) dendritic cells 7) and neoplastic intestinal epithelial cells.8) Recent studies have reported that such vesicles are present in some physiological fluids, such as bronchoalveolar lavage 9) or urine. 10) However, there is still little evidence of whether exosomes are produced in vivo.Saliva is considered to provide the first line of oral cavity defense against bacterial and viral attack. Human whole saliva contains a potent mixture of diverse components such as mucin, immunoglobulin A (IgA), proline-rich proteins and defensins, which are produced in three major paired salivary glands (parotid, submadibular and sublingual) and several minor glands. Although comprehensive proteome analyses of whole saliva have been reported recently, 12,13) the protein constituents of saliva are not fully understood.The membrane-associated serine protease dipeptidyl peptidase IV (DPP IV), which is identical to the lymphocyte surface glycoprotein CD26, cleaves dipeptides from the N-terminus of peptides with a proline or alanine residue in the penultimate position.14) CD26/DPP IV is highly expressed on fibroblasts, epithelial and endothelial cells, and specific leukocyte subsets. The extracellular protease domain of CD26/DPP IV, which is produced by proteolytic cleavage of the membrane-bound form of CD26/DPP IV, also exists in a soluble form in plasma.15) Recently, it was reported that DPP IV is released from intestinal epithelial cells into the extracellular milieu as a constituent of exosome-like vesicles. 8)More recently, our previous report revealed that DPP IV is released into snake venom in an unprocessed form, 16) suggesting that the DPP IV is associated with membrane. In addition, we have found exosome-like vesicles that carry DPP IV in snake venom.17) DPP IV activity has been found in human saliva, 18) but the mechanism of its release has not been elucidated. Snake venom is highly modified saliva that is produced by special glands of certain species of snakes. Therefore, we hypothesized that exosome-like vesicles carrying DPP IV could be present in human saliva. We demonstrate for the first time a population of vesicles in human whole saliva similar in size to the previously described exosomes. We found that these vesicles contain DPP IV, galectin-3 and IgA. MATERIALS AND METHODS MaterialsGly-Pro-4-methyl...

Extracellular presence/release of galectins from HTR-8/SVneo extravillous trophoblast cells*

“…The findings presented here are novel for gal-3 and gal-8, since no literature data regarding their presence in EVs of trophoblast origin have been reported so far. However, both gal-3 and gal-8 were found in EVs from different cell types or body fluids (Ogawa et al, 2008;Wang et al, 2012;Webber et al, 2014;Hurwitz et al, 2016).…”

Exosomes in cancer theranostic: Diamonds in the rough

“…11 Furthermore, in addition to immune cells, many other cell types have been described as exosome secretory cells such as epithelial cells, 19 neurons 20 and tumor cells. 21 Exosomes can be isolated from cell culture supernatants and can be found in numerous body fluids such as blood, 22,23 urine, 24 saliva, 25 bronchoalveolar fluid, 26 seminal fluid, 27 amniotic fluid, 28 breast milk, 29 tumor effusions 30 and cerebrospinal fluid. 31 …”

Salivary VIP concentrations are elevated in humans after acute stress

“…Another research article demonstrates the presence of exosome-like vesicles with dipeptidyl peptidase (DPP) IV activity in human saliva . Ogawa et al (2008) demonstrated that the DPP IV was able to cleave substance P and glucose-dependent insulinotropic polypeptide .…”