PC3-secreted microprotein (PSMP) or microseminoprotein is a newly discovered secreted protein whose function is currently unknown. In this study, PSMP was found to possess chemotactic ability toward monocytes and lymphocytes, and its functional receptor was identified as CCR2B. PSMP was identified as a chemoattractant protein from a PBMC chemoattractant platform screen that we established. The mature secreted PSMP was able to chemoattract human peripheral blood monocytes, PBLs, and CCR2B-expressing THP-1 cells, but not peripheral blood neutrophils, even though it does not contain the classical structure of chemokines. CCR2B was identified as one receptor for PSMP-mediated chemotaxis by screening HEK293 cells that transiently expressed classical chemokine receptors; results obtained from the chemotaxis, calcium flux, receptor internalization, and radioligand-binding assays all confirmed this finding. To further identify the major function of PSMP, we analyzed its expression profile in tissues. PSMP is highly expressed in benign prostatic hyperplasia and in some prostate cancers, and can also be detected in breast tumor tissue. In response to PSMP stimulation, phosphorylated ERK levels downstream of CCR2B signaling were upregulated in the PC3 cell line. Taken together, our data collectively suggest that PSMP is a chemoattractant protein acting as a novel CCR2 ligand that may influence inflammation and cancer development.

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Background: CCR4 is highly expressed on Th2 cells. These cells play an important role in acute inflammatory responses, including those involved in allergic rhinitis. We determined whether disrupting the CCR4 ligand interaction with CCR4 antagonist could alleviate allergic rhinitis in a mouse model. Methods: BALB/c mice were sensitized with ovalbumin and alum by intraperitoneal injection and challenged with intranasally administered ovalbumin. Compound 22, which has been reported as a novel small-molecule antagonist of CCR4, was also administered intranasally. In addition, budesonide, an efficient glucocorticoid, was used as a positive control. The effects of compound 22 were quantified by multiple parameters of allergic responses in both nasal and pulmonary tissues. Results: Compound 22 significantly improved symptoms of allergic rhinitis and suppressed levels of total IgE of serum. It dramatically reduced the levels of IL-4 in bronchoalveolar lavage fluid and also decreased the number of inflammatory cells in the fluid. The infiltration of inflammatory cells, especially eosinophils, was markedly reduced in the nasal and pulmonary tissues. The number of IL-4+ cells was also significantly reduced in these tissues. Moreover, the numbers of Foxp3+ cells and IL-17+ cells were reduced, though not to a statistically significant degree. Conclusions: In our research, CCR4 antagonists such as compound 22 were proven for the first time to alleviate murine allergic rhinitis when administered nasally. CCR4 antagonists may have therapeutic potential for the treatment of allergic rhinitis.

To find new human gene encoding protein which has potential to be chemokine like or chemokine, our laboratory has established the peripheral blood mononuclear cell (PBMC) chemoattractant platform, which includes four steps. First, we screened out 212 genes potential to be cytokines from the genes library in which the genes’ cytokine-related function was unknown or unreported. And then, we constructed the eukaryotic vectors expressing the candidate genes. And third, the proteins encoded by the candidate genes, which could be secreted, were chosen. At last, the secretive proteins were applied on the PBMC chemoattractant platform to find the protein which had the chemoattractant ability. The PBMC chemoattractant platform was based on the Boyden Chamber Assay. Among the proteins which were potential to be chemokine or chemokine like, one protein was found having the ability to chemoattract peripheral blood monocyte and lymphocyte, which was low expressed in normal tissue and detected in human breast cancer and prostate cancer. What’s more, we have found that CCR2B was the protein’s chemoattractant receptor in vitro. In consideration of CCR2B is normally expressed in lots of cancer sites, the protein which we have found may play some kind role in the procession of cancer development.