View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector Japanese Dental Science Review (2010) 46, 165—172 available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/jdsr Review article New trends in the study of podoplanin as a cell morphological regulator Yoshihiko Sawa * Department of Morphological Biology, Fukuoka Dental College, 2-15-1 Tamura, Sawara-Ku, Fukuoka 814-0193, Japan Received 7 August 2009; received in revised form 26 November 2009; accepted 13 January 2010 KEYWORDS Summary Podoplanin is a mucin-type glycoprotein firstly identified in podocytes, which is Podoplanin; homologous to the type I alveolar cell specific T1a-2 antigen and to the oncofetal antigen Cancer M2A recognized by the D2-40 antibody. Podoplanin possesses a platelet aggregation-stimulating domain causes the platelet aggregation on cancer cells by the binding activity to CLEC-2. Podoplanin also contributes to the formation of membrane-actin structures. The increased podoplanin expression is found in squamous cell carcinomas at the invasive edge. It has been reported that the podoplanin induces an actin cytoskeleton rearrangement dependent on the RhoA GTPase activation to phosphorylate ezrin and facilitates an epithelial-mesenchymal transi- tion (EMT) which induces the single cell migration of cancer cells. However, the podoplanin- expressing cancer cells often express E-cadherin and migrate in a collective manner, suggesting that there are podoplanin-induced alternative pathways for the actin cytoskeleton rearrangement independent of the RhoA activation and EMT. The strong expression of podoplanin is present in salivary gland myoepithelial cells, and in enamel epithelia and odontoblasts of the tooth germ for a bell stage. Podoplanin may act as a cell morphological regulator in normal and cancer cells. # 2010 Japanese Association for Dental Science. Published by Elsevier Ireland. Open access under CC BY-NC-ND license. Contents 1. Expression of podoplanin in the human somatic tissue ............................................. 166 1.1. Roles of podoplanin as a podocyte antigen ................................................. 166 1.2. Lymphatic endothelial cell marker, podoplanin.............................................. 166 1.3. Podoplanin expression in the oral and other tissues .......................................... 166 2. Expression of podoplanin in cancer ........................................................... 168 3. Molecular characteristics of podoplanin ........................................................ 168 3.1. Transcription of podoplanin gene ........................................................ 168 * Tel.: +81 92 801 0411; fax: +81 92 801 4909. E-mail address: [email protected]. 1882-7616 # 2010 Japanese Association for Dental Science. Published by Elsevier Ireland. Open access under CC BY-NC-ND license. doi:10.1016/j.jdsr.2010.01.003 166 Y. Sawa 3.2. Molecular biological function of podoplanin ................................................ 168 3.3. Novel aspects on the event podoplanin induces in cancer cells: EMT or not?........................ 169 References.............................................................................. 170 1. Expression of podoplanin in the human regulated by IL-3 which expressed in lymphatic but not blood somatic tissue endothelium. The endogenous IL-3 is required to maintain the lymphatic endothelial cell phenotype and appears to induce transdifferentiation of blood endothelium into lymphatic 1.1. Roles of podoplanin as a podocyte antigen endothelium [16]. Furthermore, recent study showed that the early activation of a Ras homolog gene family, member Podoplanin, also called as E11 antigen/GP36/aggrus, is a A (RhoA)-GTPase in the lymphangiogenic process, which is mucin-type 38-kDa transmembrane glycoprotein firstly iden- required for the successful establishment of the capillary tified as a 43-kd protein of the kidney glomerular epithelial network, is dependent on podoplanin expression [18].Inthe cells, podocytes [1]. Podoplanin is homologous to T1a-2 gene study for the response of lymphatic vascular systems against which encodes the type I alveolar cell specific antigen and to the infection, we have been reported that lymphatic endothe- the oncofetal antigen M2A recognized by the D2-40 antibody lium significantly increases podoplanin expression with lipo- [2—4]. The role of podoplanin has been studied in a rat model polysaccharide and lipoteichoic acid by the recognition of nephropathy by the puromycin aminonucleoside nephrosis mechanisms to pathogen-associated molecular patterns with severe proteinuria. In the kidney with nephropathy, through toll-like receptors [19—21]. podocyte foot processes are extensive flattening and podo- planin is selectively reduced to <30%. It has been thought that podoplanin plays a role in maintaining the shape of 1.3. Podoplanin expression in the oral and other podocyte foot processes and glomerular permeability tissues because of morphological alterations of cell shape with selective loss of podoplanin in the nephrosis accompanies In the oral tissue the expression of podoplanin is weakly found proteinuria [1,5—7]. in mucous epithelial cells at a basal layer and strongly in myoepithelial cells of salivary glands [22] (Fig. 1). The podo- 1.2. Lymphatic endothelial cell marker, planin expression is rarely found in acini of the parotid gland podoplanin but clearly found at the basal portion of acini in the subman- dibular and sublingual glands. The strong expression of podo- The study for the lymphatic system at a molecular biology level planin is also found at the basal portion of the intercalated made rapid progress greatly since 1999 when much break- duct, striated duct and interlobular duct in all major salivary through about lymphatic endothelial cell markers, such as glands. In the parotid gland few myoepithelial cells are on the desmoplakin, LYVE-1, Prox1, and podoplanin, has been accom- terminal portion while in the sublingual gland and subman- plished [8—11]. The discovery most major in these would be dibular gland, approximately 50% and 25% of the terminal that lymphatic development is independent of the vascular portion surface are covered by myoepithelial cells with a system development, and that lymphatic-specific homeobox number of broad and extensive cellular processes. Myoepithe- gene Prox1 induces the lymphatic endothelial development lial cells act as a contractile cell for the saliva secretion and the from embryonic veins and homozygous Prox1-null mouse cell shape varies considerably with the different glands in embryos die because of multiple developmental defects relation to the physical properties of secretions [23]. Podo- [11—15]. Prox1 is a master regulator of the podoplanin expres- planin would be a marker protein of salivary gland myoepithe- sion induced with epidermal growth factor, basic fibroblast lial cells because the podoplanin detection levels coincide growth factor, tumor necrosis factor alpha, interleukin-3, and with the distribution and the cell shape of myoepithelial cells transforming growth factor beta. Prox1 enables to reprogram specific for major salivary glands. Podoplanin may play a role in vascular endothelial cells to become podoplanin-expressing maintaining the shape of myoepithelial cell foot processes to lymphatic endothelial cells [13—16]. It has been firstly press acinar cells from the outside. reported that podoplanin is predominantly expressed by lym- The podoplanin expression is also found in the tooth germ phatic endothelium in angiosarcomas mixed endothelial phe- tissue [24] (Fig. 2). The expression is strongly found in inner notypes of blood and lymphatic capillaries [8]. Podoplanin is and outer enamel epithelia at the early bell stage while first expressed at around E11.0 in Prox1-positive lymphatic rarely in the enamel organ at the crown stage. Furthermore, progenitor cells [10]. Podoplanin(À/À) mice die at birth the podoplanin expression is rarely found in the mesenchymal because of the respiratory failure and have defects in lym- cells of dental papilla except for odontoblasts. The strong phatic formation with diminished lymphatic transport, con- expression of podoplanin in odontoblasts is sustained during a genital lymphedema and dilation of lymphatic vessels, but not dentin formative period and diminished at the root formation have defects in blood vessel pattern formation. Podoplanin stage. It has been reported that podoplanin promotes the promotes lymphatic endothelial cell adhesion and regulates plasma membrane extension and the actin cytoskeleton the lymphatic vasculature formation [10]. The immunoelec- rearrangement involved in cell mobility [25—27]. Podoplanin tron microscopic study has demonstrated that podoplanin is may be involved in the cell shape formation of odontoblasts expressed on the luminal side of lymphatic vessels and rarely and in the migration of epithelial cells into mesenchymal on the basal side [17]. The podoplanin and Prox1 expression is cells like cancer cells. Podoplanin as a morphological regulator 167 Figure 1 Podoplanin expression in the mouse oral tissues. (A and D) Serial sections of the tongue tissue. Reaction products of anti- podoplanin with green fluorescence are found in the mucosal epithelial cells at a basal layer (asterisk), myoepithelial cells of lingual glands (arrowheads), and lymphatic vessels (arrow). (B and E) Serial sections of parotid gland. Podoplanin expression