A major challenge in the application of structure-based drug design methods to proteins belonging to the superfamily of G protein-coupled receptors (GPCRs) is the paucity of structural information (1). The 19 chemokine receptors, belonging to the Class A family of GPCRs, are important drug targets not only for autoimmune diseases like multiple sclerosis but also for the blockade of human immunodeficiency virus type 1 entry (2). Using the MembStruk computational method (3), we predicted the three-dimensional structure of the human CCR1 receptor. In addition, we predicted the binding site of the small molecule CCR1 antagonist BX 471, which is currently in Phase II clinical trials (4). Based on the predicted antagonist binding site we designed 17 point mutants of CCR1 to validate the predictions. Subsequent competitive ligand binding and chemotaxis experiments with these mutants gave an excellent correlation to these predictions. In particular, we find that Tyr-113 and Tyr-114 on transmembrane domain 3 and Ile-259 on transmembrane 6 contribute significantly to the binding of BX 471. Finally, we used the predicted and validated structure of CCR1 in a virtual screening validation of the Maybridge data base, seeded with selective CCR1 antagonists. The screen identified 63% of CCR1 antagonists in the top 5% of the hits. Our results indicate that rational drug design for GPCR targets is a feasible approach.Chemokines belong to a large family of small, chemotactic cytokines that regulate the trafficking of immune cells (5) by binding to cell surface receptors belonging to the GPCR 3 superfamily (5). CCR1, the first CC chemokine receptor to be identified, responds to a number of ligands, including MIP-1␣ (CCL3) and RANTES (regulated on activation normal T cell expressed and secreted) (CCL5) (6, 7). The strong association with a wide variety of autoimmune and pro-inflammatory diseases has made the CCR1 protein an attractive therapeutic target, and Berlex has developed a potent, specific, orally available antagonist, BX 471, currently in a Phase II clinical trial (8).The CCR1 antagonist program that yielded the clinical compound BX 471 followed a traditional drug discovery approach starting with high throughput screening of large compound libraries (9). Although high throughput screening is a main pillar of drug-finding programs in the pharmaceutical industry, it has recently been supplemented by in silico methods to maximize the probability of finding attractive novel leads. Structurebased in silico approaches have been challenging for GPCRs, because only one experimental GPCR structure, that of bovine rhodopsin, with only ϳ20% sequence identity to CCR1 (10), has been reported. Recent developments in GPCR structure prediction methods show great potential for structure-based drug design and identifying novel hits from virtual screens (11)(12)(13)(14)(15).In this communication we report a significant test of the computational method MembStruk by predicting the structure of CCR1. Further, we scanned the entire predicted struc...

The chemokine receptor CCR1 and its principal ligand, CCL3/MIP-1␣, have been implicated in the pathology of several inflammatory diseases including rheumatoid arthritis, multiple sclerosis, and asthma. As such, these molecules are the focus of much research with the ultimate aim of developing novel therapies. We have described previously a non-competitive small molecule antagonist of CCR1 (UCB 35625), which we hypothesized interacted with amino acids located within the receptor transmembrane (TM) helices (Sabroe, I., Peck, M. J., Jan Van Keulen, B., Jorritsma, A., Simmons, G., Clapham, P. R., Williams, T. J., and Pease, J. E. (2000) J. Biol. Chem. 275, 25985-25992). Here we describe an approach to identifying the mechanism by which the molecule antagonizes CCR1. Thirty-three point mutants of CCR1 were expressed transiently in L1.2 cells, and the cells were assessed for their capacity to migrate in response to CCL3 in the presence or absence of UCB 35625. Cells expressing the mutant constructs Y41A (TM helix 1, or TM1), Y113A (TM3), and E287A (TM7) were responsive to CCL3 but resistant to the antagonist, consistent with a role for the TM helices in CCR1 interactions with UCB 35625. Subsequent molecular modeling successfully docked the compound with CCR1 and suggests that the antagonist ligates TM1, 2, and 7 of CCR1 and severely impedes access to TM2 and TM3, a region thought to be perturbed by the chemokine amino terminus during the process of receptor activation. Insights into the mechanism of action of these compounds may facilitate the development of more potent antagonists that show promise as future therapeutic agents in the treatment of inflammatory disease.

IntroductionMacrophages are essential cells of the immune system that alter their inflammatory profile depending on their microenvironment. Alternative polyadenylation in the 3’UTR (3’UTR-APA) and intronic polyadenylation (IPA) are mechanisms that modulate gene expression, particularly in cancer and activated immune cells. Yet, how polarization and colorectal cancer (CRC) cells affect 3’UTR-APA and IPA in primary human macrophages was unclear.MethodsIn this study, we isolated primary human monocytes from healthy donors, differentiated and polarized them into a pro-inflammatory state and performed indirect co-cultures with CRC cells. ChrRNA-Seq and 3’RNA-Seq was performed to quantify gene expression and characterize new 3’UTR-APA and IPA mRNA isoforms.ResultsOur results show that polarization of human macrophages from naïve to a pro-inflammatory state causes a marked increase of proximal polyA site selection in the 3’UTR and IPA events in genes relevant to macrophage functions. Additionally, we found a negative correlation between differential gene expression and IPA during pro-inflammatory polarization of primary human macrophages. As macrophages are abundant immune cells in the CRC microenvironment that either promote or abrogate cancer progression, we investigated how indirect exposure to CRC cells affects macrophage gene expression and 3’UTR-APA and IPA events. Co-culture with CRC cells alters the inflammatory phenotype of macrophages, increases the expression of pro-tumoral genes and induces 3’UTR-APA alterations. Notably, some of these gene expression differences were also found in tumor-associated macrophages of CRC patients, indicating that they are physiologically relevant. Upon macrophage pro-inflammatory polarization, SRSF12 is the pre-mRNA processing gene that is most upregulated. After SRSF12 knockdown in M1 macrophages there is a global downregulation of gene expression, in particular in genes involved in gene expression regulation and in immune responses.DiscussionOur results reveal new 3’UTR-APA and IPA mRNA isoforms produced during pro-inflammatory polarization of primary human macrophages and CRC co-culture that may be used in the future as diagnostic or therapeutic tools. Furthermore, our results highlight a function for SRSF12 in pro-inflammatory macrophages, key cells in the tumor response.

Macrophages are essential cells of the immune system that alter their inflammatory profile depending on their microenvironment. Alternative polyadenylation in the 3prime UTR (3prime UTR-APA) and intronic polyadenylation (iPA) are mechanisms that modulate gene expression, in particular in cancer and activated immune cells. Yet, how polarization and colorectal cancer (CRC) cells microenvironment affect 3prime UTR-APA and iPA in primary human macrophages remains unknown. Here, primary human monocytes were isolated from healthy donors, differentiated and polarized into a pro-inflammatory state and ChrRNA-Seq and 3prime RNA-Seq were performed to quantify gene expression and characterize new 3prime UTR-APA and iPA mRNA isoforms. Our results show that polarization of human macrophages from naive to a pro-inflammatory state causes a marked increase both in proximal polyA site selection in the 3prime UTR and in iPA events, in genes relevant for macrophage functions. Additionally, we found a negative correlation between differential gene expression and iPA during pro-inflammatory polarization of primary human macrophages. As macrophages are abundant immune cells in the CRC microenvironment that either promote or abrogate cancer progression, we investigated how indirect exposure to CRC cells affects macrophage gene expression and 3prime UTR-APA and iPA mRNA events. Co-culture with CRC cells alters the inflammatory phenotype of macrophages, increases the expression of pro-tumoral genes and induce 3prime UTR-APA alterations. Notably, some of these gene expression differences were also found in tumor-associated macrophages of CRC patients, indicating that they are physiological relevant. Upon macrophage pro-inflammatory polarization SRSF12 is the pre-mRNA processing gene that is most upregulated. After SRSF12 knockdown in M1 macrophages there is a global downregulation of gene expression, in particular in genes involved in gene expression regulation and in immune responses. Our results reveal new 3prime UTR-APA and iPA mRNA isoforms produced during pro-inflammatory polarization of primary human macrophages and CRC co-culture that may be used in the future as diagnostic or therapeutic tools.