PubMed · 10469221
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M Sur, K Cooper. 1999. PNETs everywhere.. https://doi.org/10.1046/j.1365-2559.1999.0781a.x
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We studied the role of lipid rafts and actin cytoskeleton in CD99-mediated signaling to elucidate the mechanism of protein transport upon CD99 engagement. CD99 engagement in Jurkat cells elicited the exocytic transport of GM1 as well as several surface molecules closely related with CD99 functions. In addition, CD99 molecules were rapidly incorporated into lipid rafts and appeared to rearrange the actin cytoskeleton upon CD99 stimulation. Association of CD99 with actin cytoskeleton was inhibited by methyl-beta-cyclodextrin, while CD99-mediated GM1 clustering was inhibited by cytochalasin D. Therefore, we suggest that CD99 may play a role in the vesicular transport of transmembrane proteins and lipid rafts from the intracellular location to the cell surface, possibly by effecting actin cytoskeleton reorganization.
Human CD99 (MIC2) is a 32 kDa cell surface protein and its encoding gene is localized to the pseudoautosomal regions of both Xp and Yp chromosomes. Although sequences of several genes such as human PBDX and MIC2R are known to be related to that of CD99, the murine counterpart of CD99 has not been reported. Here we have identified a novel CD99 mouse paralog, named as CD99L2 (CD99 antigen-like 2), and its human, rat and zebrafish genes. Unlike the rapidly evolved CD99 gene, these CD99L2 genes were highly conserved among those species. However, the genomic organization of human and mouse CD99L2 genes showed a difference in their exon numbers possibly due to exon duplication during evolution. In addition, comparative analysis of the cDNA sequences identified the presence of variants in the region around the exons 3 and 4 even within a species due to a differential splicing event, resulting in species-specific patterns in their transcripts. As determined by in situ hybridization analysis, the CD99L2 gene appeared to be expressed particularly high in neuronal cells despite its ubiquitous distribution. The highly expression on neuronal cells without any variations between species reflects a dominant role of this molecule during neural development. Amino acid sequence alignment revealed five putative functional regions highly conserved between CD99L2 and CD99, indicating a close relationship between the two genes. Moreover, human and mouse CD99L2 were located on their X chromosomes, respectively, whereas the zebrafish mic2l1 gene was in the LG7 chromosome. These observations support the inference that the evolutionary conserved gene, CD99L2, originated from a common ancestor gene of CD99, and its high conservation among species implies at least some essential function.
The objective was to investigate two cases of solitary fibrous tumor (SFT) of oral mucosa, emphasizing the differential diagnosis with one case of oral hemangiopericytoma (HPC), in terms of their morphological and immunohistochemical features. Solitary fibrous tumors showed cellularity and collagenization varying from area to area, focal perivascular hyalinization, scattered giant nuclei cells and abundant mast cells throughout the tumor. The hemangiopericytoma case exhibited thin-walled and dilated vessels lined with flat endothelial cells, identified by "staghorn appearance". Tumoral cells of solitary fibrous tumor exhibited immunohistochemical positivity for CD34, as well as endothelial cells. The hemangiopericytoma was positive only in endothelial cells. In solitary fibrous tumor, alpha-smooth muscle actin, h-caldesmon and laminin stained the wall vessels. In hemangiopericytoma, on the other hand, the wall vessels were positive only for laminin, which staining was also observed in perivascular tumoral cells. The morphological and immunohistochemical differences observed allowed us to infer these lesions constitute distinct entities.