Cell communication systems based on polypeptide ligands use transmembrane receptors to transmit signals across the plasma membrane. In their biogenesis, receptors depend on the endoplasmic reticulum (ER)-Golgi system for folding, maturation, transport and localization to the cell surface. ER stress, caused by protein overproduction and misfolding, is a well-known pathology in neurodegeneration, cancer and numerous other diseases. How ER stress affects cell communication via transmembrane receptors is largely unknown. In disease models of multiple myeloma, chronic lymphocytic leukemia and osteogenesis imperfecta, we show that ER stress leads to loss of the mature transmembrane receptors FGFR3, ROR1, FGFR1, LRP6, FZD5 and PTH1R at the cell surface, resulting in impaired downstream signaling. This is caused by downregulation of receptor production and increased intracellular retention of immature receptor forms. Reduction of ER stress by treatment of cells with the chemical chaperone tauroursodeoxycholic acid or by expression of the chaperone protein BiP resulted in restoration of receptor maturation and signaling. We show a previously unappreciated pathological effect of ER stress; impaired cellular communication due to altered receptor processing. Our findings have implications for disease mechanisms related to ER stress and are particularly important when receptor-based pharmacological approaches are used for treatment.

• Keywords
• ER, Endoplasmic reticulum, Impaired, Receptor, Signaling, Stress, Transmembrane,
• MeSH
• Endoplasmic Reticulum Chaperone BiP MeSH
• Taurochenodeoxycholic Acid pharmacology   MeSH
• Humans MeSH
• Cell Line, Tumor MeSH
• Receptors, Cell Surface * metabolism   MeSH
• Signal Transduction * drug effects   MeSH
• Endoplasmic Reticulum Stress * drug effects   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Endoplasmic Reticulum Chaperone BiP MeSH
• Taurochenodeoxycholic Acid MeSH
• Receptors, Cell Surface * MeSH
• ursodoxicoltaurine MeSH Browser

Chronic lymphocytic leukemia is a disease with up-regulated expression of the transmembrane tyrosine-protein kinase ROR1, a member of the Wnt/planar cell polarity pathway. In this study, we identified COBLL1 as a novel interaction partner of ROR1. COBLL1 shows clear bimodal expression with high levels in chronic lymphocytic leukemia patients with mutated IGHV and approximately 30% of chronic lymphocytic leukemia patients with unmutated IGHV. In the remaining 70% of chronic lymphocytic leukemia patients with unmutated IGHV, COBLL1 expression is low. Importantly, chronic lymphocytic leukemia patients with unmutated IGHV and high COBLL1 have an unfavorable disease course with short overall survival and time to second treatment. COBLL1 serves as an independent molecular marker for overall survival in chronic lymphocytic leukemia patients with unmutated IGHV. In addition, chronic lymphocytic leukemia patients with unmutated IGHV and high COBLL1 show impaired motility and chemotaxis towards CCL19 and CXCL12 as well as enhanced B-cell receptor signaling pathway activation demonstrated by increased PLCγ2 and SYK phosphorylation after IgM stimulation. COBLL1 expression also changes during B-cell maturation in non-malignant secondary lymphoid tissue with a higher expression in germinal center B cells than naïve and memory B cells. Our data thus suggest COBLL1 involvement not only in chronic lymphocytic leukemia but also in B-cell development. In summary, we show that expression of COBLL1, encoding novel ROR1-binding partner, defines chronic lymphocytic leukemia subgroups with a distinct response to microenvironmental stimuli, and independently predicts survival of chronic lymphocytic leukemia with unmutated IGHV.

• MeSH
• Survival Analysis MeSH
• Leukemia, Lymphocytic, Chronic, B-Cell classification   diagnosis   genetics   mortality   MeSH
• Humans MeSH
• Mutation MeSH
• Cell Movement MeSH
• Cell Polarity MeSH
• Prognosis MeSH
• Wnt Signaling Pathway MeSH
• Receptor Tyrosine Kinase-like Orphan Receptors metabolism   MeSH
• Immunoglobulin Heavy Chains genetics   MeSH
• Transcription Factors metabolism   MeSH
• Immunoglobulin Variable Region genetics   MeSH
• Protein Binding MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• COBLL1 protein, human MeSH Browser
• ROR1 protein, human MeSH Browser
• Receptor Tyrosine Kinase-like Orphan Receptors MeSH
• Immunoglobulin Heavy Chains MeSH
• Transcription Factors MeSH
• Immunoglobulin Variable Region MeSH

PURPOSE: ROR1, a receptor in the noncanonical Wnt/planar cell polarity (PCP) pathway, is upregulated in malignant B cells of chronic lymphocytic leukemia (CLL) patients. It has been shown that the Wnt/PCP pathway drives pathogenesis of CLL, but which factors activate the ROR1 and PCP pathway in CLL cells remains unclear. EXPERIMENTAL DESIGN: B lymphocytes from the peripheral blood of CLL patients were negatively separated using RosetteSep (StemCell) and gradient density centrifugation. Relative expression of WNT5A, WNT5B, and ROR1 was assessed by quantitative real-time PCR. Protein levels, protein interaction, and downstream signaling were analyzed by immunoprecipitation and Western blotting. Migration capacity of primary CLL cells was analyzed by the Transwell migration assay. RESULTS: By analyzing the expression in 137 previously untreated CLL patients, we demonstrate that WNT5A and WNT5B genes show dramatically (five orders of magnitude) varying expression in CLL cells. High WNT5A and WNT5B expression strongly associates with unmutated IGHV and shortened time to first treatment. In addition, WNT5A levels associate, independent of IGHV status, with the clinically worst CLL subgroups characterized by dysfunctional p53 and mutated SF3B1. We provide functional evidence that WNT5A-positive primary CLL cells have increased motility and attenuated chemotaxis toward CXCL12 and CCL19 that can be overcome by inhibitors of Wnt/PCP signaling. CONCLUSIONS: These observations identify Wnt-5a as the crucial regulator of ROR1 activity in CLL and suggest that the autocrine Wnt-5a signaling pathway allows CLL cells to overcome natural microenvironmental regulation.

• MeSH
• Autocrine Communication physiology   MeSH
• B-Lymphocytes metabolism   MeSH
• Chemotaxis physiology   MeSH
• Leukemia, Lymphocytic, Chronic, B-Cell metabolism   MeSH
• HEK293 Cells MeSH
• Humans MeSH
• Cell Movement physiology   MeSH
• Wnt-5a Protein MeSH
• Wnt Proteins metabolism   MeSH
• Proto-Oncogene Proteins metabolism   MeSH
• Gene Expression Regulation, Neoplastic physiology   MeSH
• Wnt Signaling Pathway physiology   MeSH
• Receptor Tyrosine Kinase-like Orphan Receptors metabolism   MeSH
• Up-Regulation physiology   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Intramural MeSH
• Names of Substances
• Wnt-5a Protein MeSH
• Wnt Proteins MeSH
• Proto-Oncogene Proteins MeSH
• ROR1 protein, human MeSH Browser
• Receptor Tyrosine Kinase-like Orphan Receptors MeSH
• WNT5A protein, human MeSH Browser
• WNT5B protein, human MeSH Browser