A number of orphan G-protein coupled receptors (GPR) have been reported as putative chemokine receptors. One previously reported orphan receptor is an incomplete PCR clone, called GPR2. Here we report the cloning of full-length human (h)GPR2 and mouse (m)GPR2 cDNAs, and the identification of GPR2 as a receptor for a novel CC chemokine called ESkine. hGPR2 is expressed at high levels in testis and small intestine, and at lower levels in other tissues. mGPR2 was expressed at high levels in small intestine, colon, lymph nodes, and Peyer’s patches and at lower levels in thymus and spleen. Stimulation of L1.2/hGPR2 transfectants with hESkine induced their migration and resulted in intracellular calcium mobilization. These results provide evidence that GPR2 is a specific receptor for ESkine. We propose that GPR2 be renamed as CCR10. The expression pattern of mGPR2/CCR10 suggests that it may play a role in the homing/trafficking of leukocytes within intestinal and lymphoid environments.
We have previously shown that the β-chemokine ESkine/CCL27 is differentially spliced to produce two alternative forms. One is a secreted chemokine (ESkine), whereas the other (PESKY) lacks a signal peptide and is translocated to the nucleus. The role of this nuclear-targeted chemokine has not so far been defined, and it was the purpose of this study to examine this chemokine variant in more depth. To identify the region of PESKY involved in the nuclear translocation we tagged fragments with enhanced green fluorescent protein and expressed them in Chinese hamster ovary cells. We show PESKY nuclear translocation to be dependent on C-terminal residues that are shared with the signal peptide-bearing variant ESkine. Indeed we further demonstrate that ESkine can also use these C-terminal residues to enter the nucleus of cells following receptor (CCR10)-mediated internalization. To examine biological roles for PESKY we have overexpressed it in 3T3 cells. Such overexpression results in marked cytoskeletal rearrangements that are coincident with a radical reorganization of the cellular actin cytoskeleton. Microarray analyses and Ab neutralization studies indicate that these changes are mediated in part by insulin-like growth factor-1. Furthermore, monolayer wounding assays indicate that PESKY expression correlates with markedly increased migratory capacity. Thus, it is our contention that nuclear PESKY and ESkine both enter the nucleus by either intracrine or paracrine mechanisms and may facilitate cellular migration by inducing actin cytoskeletal relaxation. Therefore, nuclear ESkine/PESKY represents a novel paradigm for chemokine function.
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