Mapping of the genes for four members of the transmembrane 4 superfamily: mouse Cd9, Cd63, Cd81, and Cd82

Cocaine-Specific Effects on Exosome Biogenesis in Microglial Cells

Cocaine is a highly addictive stimulant and a well-known drug, with multiple effects on physiology. Cocaine can have direct effects on all cell types in the brain, including microglia. Microglia can be activated by other conditions, such as infection, inflammation, or injury. However, how cocaine regulates microglia and the influence of cocaine on microglial-derived exosomes remains unknown. Exosomes are nanovesicles that are responsible for intercellular communications, signaling, and trafficking necessary cargo for cell homeostasis. In this study, we hypothesized that cocaine affects exosome biogenesis and composition in BV2 microglial cells. BV2 microglial cells were cultured in exosome-depleted RPMI-1640 media and were treated according to the experimental designs. We observed that cell viability decreased by 11% at 100 µM cocaine treatment but was unaffected at other concentrations. After treatments, the exosomes were isolated from the condition media. Purified exosomes were characterized and quantified using transmission electron microscope (TEM) and nanoparticle tracking analysis (NTA). By NTA, there was a significant decrease in particles/mL after cocaine treatment. There was a 39.5%, 58.1%, 32.3% and 28.1% decrease in particles/mL at 100 nM, 1 μM, 10 μM and 100 μM cocaine, respectively. The characterization of exosomes and exosomal protein was performed by western/dot blot analyses. Tetraspanins CD11b, CD18 and CD63 were relatively unchanged after cocaine treatment. The heat shock proteins (Hsps), Hsp70 and Hsp90, were both significantly increased at 10 μM and 100 μM, but only hsp70 was significantly increased at 10 nM. The Rab proteins were assessed to investigate their role in cocaine-mediated exosomal decrease. Rab11 was significantly decreased at 10 nM, 100 nM, 1 μM, 10 μM and 100 μM by 15%, 28%, 25%, 38% and 22%, respectively. Rab27 was decreased at all concentrations but only significantly decreased at 100 nM, 1 μM and 100 μM cocaine by 21%, 24% and 23%, respectively. Rab35 had no significant changes noted when compared to control. Rab7 increased at all cocaine concentrations but only a significant increase in expression at 100 nM and 10 μM by 1.32-fold and 1.4-fold increase. Cocaine was found to alter exosome biogenesis and composition in BV2 microglial cells. Western and dot blot analyses verified the identities of purified exosomes, and the specific protein compositions of exosomes were found to change in the presence of cocaine. Furthermore, cocaine exposure modulated the expression of exosomal proteins, such as Hsps and Rab GTPases, suggesting the protein composition and formation of microglial-derived exosomes were regulated by cocaine.

Characterisation of the mouse homologue of CD151 (PETA-3/SFA-1); genomic structure, chromosomal localisation and identification of 2 novel splice forms

CD151 (PETA-3/SFA-1) is a member of the Transmembrane 4 Superfamily (TM4SF) of cell-surface proteins and, like other TM4SF members CD9 and CD63, is expressed by platelets, megakaryocytes and endothelial cells. The precise function of CD151 is unknown however complexes containing CD151 and beta1 integrins have been isolated from a number of cell systems and studies using anti-CD151 monoclonal antibodies have suggested a role in transmembrane signalling and cell adhesion. To further investigate the function of CD151 we have determined the genomic organisation of mouse CD151 (Cd151). Cd151 spans 4 kb and contains six coding region exons. Using 5' RACE and reverse transcriptase-polymerase chain reaction (RT-PCR) we have identified three 5' UTR splice variants which arise through alternate splicing of three exons. Splice variants were detected in a number of mouse tissues by RT-PCR. Analysis of the Cd151 genomic structure reveals a high degree of structural conservation with other TM4SF molecules supporting the theory that family members have arisen from gene duplication of a common ancestral gene. Cd151 maps to chromosome 7, in close linkage to the p gene (OCA2 in humans), and helps define a boundary in the human/mouse homology relationships.

Association between the rat homologue of CO-029, a metastasis-associated tetraspanin molecule and consumption coagulopathy

Recently, we have described a panel of metastasis-associated antigens in the rat, i.e., of molecules expressed on metastasizing, but not on nonmetastasizing tumor lines. One of these molecules, recognized by the monoclonal antibody D6.1 and named accordingly D6. 1A, was found to be abundantly expressed predominantly on mesenchyme-derived cells. The DNA of the antigen has been isolated and cloned. Surprisingly, the gene product proved to interfere strongly with coagulation. The 1.182-kb cDNA codes for a 235-amino acid long molecule with a 74.2% homology in the nucleotide and a 70% homology in the amino acid sequence to CO-029, a human tumor-associated molecule. According to the distribution of hydrophobic and hydrophilic amino acids, D6.1A belongs to the tetraspanin superfamily. Western blotting of D6.1A-positive metastasizing tumor lines revealed that the D6.1A, like many tetraspanin molecules, is linked to further membrane molecules, one of which could be identified as alpha6beta1 integrin. Transfection of a low-metastasizing tumor cell line with D6.1A cDNA resulted in increased metastatic potential and provided a clue as to the functional role of D6.1A. We noted massive bleeding around the metastases and, possibly as a consequence, local infarctions predominantly in the mesenteric region and all signs of a consumption coagulopathy. By application of the D6.1 antibody the coagulopathy was counterregulated, though not prevented. It has been known for many years that tumor growth and progression is frequently accompanied by thrombotic disorders. Our data suggest that the phenomenon could well be associated with the expression of tetraspanin molecules.