title: Conservation of a platelet activating domain of Aggrus/podoplanin as a platelet aggregation-inducing factor.
abstract: Human Aggrus/podoplanin is an identified platelet aggregation-inducing factor of cancer cells, which is also known as a specific marker of lymphatic endothelium. Human Aggrus was known to be expressed in seminoma, squamous cell carcinoma, malignant mesothelioma, sarcomas and several brain tumors. In our previous studies, the sialylated O-glycan of human and mouse Aggrus were shown to be critical for its platelet aggregation-inducing activity in the experiments using the glycosylation-deficient Chinese hamster ovary (CHO) cell lines. We newly cloned Aggrus homologues from rat, hamster, dog and bovine cDNAs, in addition to the human and mouse cDNAs, and confirmed there are three tandem repeats of the platelet aggregation-stimulating (PLAG) domain in Aggrus, which were conserved in all homologues. We found that bovine Aggrus has a sporadic deletion mutation in the first PLAG domain, and lacks platelet aggregation-inducing activity. We introduced point mutation in the PLAG domain of Aggrus and showed that either the first or last PLAG domain is critical for activity, but not the middle domain. In addition, we studied the molecular evolutionary process of the PLAG domain of Aggrus. The PLAG domain and its activity appeared after the divergence of avians and mammals. In conclusion, we provide evidence that Aggrus homologues conserved the segment of EDxxVTPG in their extracellular domain which are critical for their platelet aggregation-inducing activities.
authors.affiliation: Department of Experimental and Forensic Pathology, Yamagata University School of Medicine, 2-2-2, Iida-nishi, Yamagata 990-9585, Japan. mk-kaneko@aist.go.jp
authors.forename: Mika Kato
authors.initials: MK
authors.lastname: Kaneko
authors.forename: Yukinari
authors.initials: Y
authors.lastname: Kato
authors.forename: Takashi
authors.initials: T
authors.lastname: Kitano
authors.forename: Motoki
authors.initials: M
authors.lastname: Osawa
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D002417:Cattle; D003001:Cloning, Molecular; D017124:Conserved Sequence; D006224:Cricetinae; D018076:DNA, Complementary / Q000235:genetics; D004285:Dogs; D006801:Humans; D066298:In Vitro Techniques; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000235:genetics* / Q000502:physiology; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D010802:Phylogeny; D010972:Platelet Activating Factor / Q000737:chemistry* / Q000235:genetics* / Q000502:physiology; D010974:Platelet Aggregation; D017434:Protein Structure, Tertiary; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014162:Transfection; D000098853:Podoplanin
chemical_list: D018076:DNA, Complementary; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D010972:Platelet Activating Factor; D011994:Recombinant Proteins; C490441:Pdpn protein, mouse; D000098853:Podoplanin; C117468:PDPN protein, human; C092025:Pdpn protein, rat