CK2.3, a mimetic peptide of BMPRIa, is a potential activator of osteoblast differentiation and activity
Date
2019
Authors
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Publisher
University of Delaware
Abstract
Osteoporosis, often referred to as OP, is a disease that is characterized by low bone mineral density. This decrease in bone mineral density leaves the bone more fragile and porous. This fragility in bone is due to an imbalance between the bone forming cells, osteoblasts, and the bone reabsorbing cells, osteoclasts. With the bone being more fragile, OP patients are more susceptible to fractures and the risk of fracturing a bone increases with age. Approximately 1 in 2 women and 1 in 4 men over the age of 50 will break a bone due to OP and an estimated 20% of those who suffer hip fractures die within a year due to complications. ☐ Despite the ever-constant presence of osteoporosis, mortality rates for this disease remain unchanged, demonstrating the ineffectiveness of current treatments on the market. The Nohe laboratory has demonstrated previously a novel Bone Morphogenetic Protein Receptor Type Ia (BMPRIa) interaction with Casein Kinase 2 (CK2) and upon BMP2 binding to the serine/threonine kinase receptor complex, CK2 dissociates from BMPRIa allowing the phosphorylation of downstream signals (Bragdon et al., 2010). Using a prosite search, the Nohe laboratory has identified three potential BMPRIa CK2 interaction sites. The Nohe laboratory has developed three mimetic peptides (CK2.3, CK2.2, and CK2.1) that encompass the site-specific sequences that could block the interaction of CK2 with BMPRIa. ☐ In this study, I investigated the ability of CK2.3 to induce the activation and differentiation of preosteoblasts and osteoblasts in vivo and in vitro. In mice, CK2.3 increased OC and ALP expression levels in a dose dependent manner. This trend was only seen in mice femurs that were extracted 4 weeks post initial injection. It was not seen in 1 week and 2 weeks post initial injection. The increase in the expression of these two markers was not caused by cellular proliferation but rather differentiation and activation. ☐ Also, in this study, I investigated CK2.3s’ ability to increase ALP and OC expression intensities in undifferentiated, 1 week differentiated, 2 weeks differentiated and 4 weeks differentiated C2C12 cells. C2C12 cells are a murine myoblast cell that can differentiate into osteoblasts under the proper conditions. Differentiated and undifferentiated cells were stimulated with PBS, CK2.3 or BMP2 and it was hypothesized that CK2.3 would produce results similar to those of BMP2. Through the use of immunofluorescent staining and imaging, I was able to show that CK2.3 does increase the level of these marker in comparison to PBS and in some cases to BMP2 as well. ☐ CK2.3 may regulate BMPRIa downstream signaling for the initiation of bone formation but the signaling cascade still needs to be properly understood. Understanding the signaling pathway could help identify molecular targets that are necessary for inducing bone growth. Given the research I have presented, CK2.3 provides a unique opportunity to identify targets that can be used as a therapeutic treatment for osteoporosis.