Evidence for Interaction Between CTHRC1 and the Extracellular Domain of TIMD4
Abstract
Collagen Triple Helix Repeat Containing 1 (CTHRC1) is a protein that functions as a signaling molecule in cells. Studies have shown that it plays roles in tissue repair, arterial remodeling, bone formation, and metabolic processes. Despite extensive research into biological functions, a receptor for CTHRC1 has not yet been identified. Identifying this receptor is an important step toward understanding the molecular mechanisms and could ultimately support the development of targeted therapeutic strategies. RNA sequencing revealed that T-cell/transmembrane, immunoglobulin, and mucin domain–containing 4 (TIMD4) was highly upregulated in cells that bind CTHRC1. TIMD4 is a phosphatidylserine receptor that encodes the transmembrane protein TIM-4, which is typically expressed in a subset of immune cells. To investigate a potential interaction between this protein and CTHRC1, a series of binding assays were conducted using immunohistochemistry and confocal microscopy. An immunoprecipitation type assay was then performed with the extracellular domain of TIMD4 fused to the Fc domain of mouse IgG2a. Confocal microscopy of TIMD4 transfected cells incubated with CTHRC1 revealed prominent co-localization of the fluorescently labeled antibodies targeting CTHRC1 and TIMD4, indicating a possible interaction between the two proteins. However, a small amount of co-localization was also observed in cells not incubated with CTHRC1. This unexpected signal was hypothesized to result from the presence of CTHRC1 in the serum added to the culture medium of the hybridoma cells producing the anti-CTHRC1 immunoglobulin. This theory was confirmed via Western blot analysis. Combining CTHRC1 with the TIMD4-Fc fusion protein in solution followed by protein G purification and Western blot analysis demonstrated co-purification of the two proteins. This result further confirmed that the extracellular domain of TIMD4 binds CTHRC1. This study provided evidence that CTHRC1 interacts with the extracellular domain of TIMD4, indicating that TIMD4 may function as a receptor for CTHRC1. Identifying the receptor for CTHRC1 would be a pivotal step toward understanding the molecular mechanisms underlying CTHRC1’s biological functions. Additionally, this discovery could enable researchers to more precisely target CTHRC1 and regulate its activity. Further binding experiments using the purified CTHRC1 antibody produced under serum-free conditions will be necessary to confirm these findings.
Evidence for Interaction Between CTHRC1 and the Extracellular Domain of TIMD4
Collagen Triple Helix Repeat Containing 1 (CTHRC1) is a protein that functions as a signaling molecule in cells. Studies have shown that it plays roles in tissue repair, arterial remodeling, bone formation, and metabolic processes. Despite extensive research into biological functions, a receptor for CTHRC1 has not yet been identified. Identifying this receptor is an important step toward understanding the molecular mechanisms and could ultimately support the development of targeted therapeutic strategies. RNA sequencing revealed that T-cell/transmembrane, immunoglobulin, and mucin domain–containing 4 (TIMD4) was highly upregulated in cells that bind CTHRC1. TIMD4 is a phosphatidylserine receptor that encodes the transmembrane protein TIM-4, which is typically expressed in a subset of immune cells. To investigate a potential interaction between this protein and CTHRC1, a series of binding assays were conducted using immunohistochemistry and confocal microscopy. An immunoprecipitation type assay was then performed with the extracellular domain of TIMD4 fused to the Fc domain of mouse IgG2a. Confocal microscopy of TIMD4 transfected cells incubated with CTHRC1 revealed prominent co-localization of the fluorescently labeled antibodies targeting CTHRC1 and TIMD4, indicating a possible interaction between the two proteins. However, a small amount of co-localization was also observed in cells not incubated with CTHRC1. This unexpected signal was hypothesized to result from the presence of CTHRC1 in the serum added to the culture medium of the hybridoma cells producing the anti-CTHRC1 immunoglobulin. This theory was confirmed via Western blot analysis. Combining CTHRC1 with the TIMD4-Fc fusion protein in solution followed by protein G purification and Western blot analysis demonstrated co-purification of the two proteins. This result further confirmed that the extracellular domain of TIMD4 binds CTHRC1. This study provided evidence that CTHRC1 interacts with the extracellular domain of TIMD4, indicating that TIMD4 may function as a receptor for CTHRC1. Identifying the receptor for CTHRC1 would be a pivotal step toward understanding the molecular mechanisms underlying CTHRC1’s biological functions. Additionally, this discovery could enable researchers to more precisely target CTHRC1 and regulate its activity. Further binding experiments using the purified CTHRC1 antibody produced under serum-free conditions will be necessary to confirm these findings.
