Study On The Maturation Of BMP6 Propeptide And Its Mechanism Of Action

BMP6(Bone Morphogenetic Protein 6)is an important member of the BMP protein family.Its C-terminal TGF-? domain is conserved,while the N-terminal propeptide domain sequence differs greatly.The biological significance of this difference is not yet clear.As a member of the transforming growth factor ?(TGF-?)superfamily,BMPs are involved in the regulation of a variety of physiological processes,including embryonic development,bone formation,iron metabolism,and cancer.Through overexpression of BMP6 propeptide to explore its function,we found that contrary to the function of full-length BMP6,both zebrafish and human BMP6 propeptide inhibit osteoblast differentiation.Through Western blot detection,we found that there is a cut point at the N-terminus of the human BMP6 propeptide,and there are two cut points at the N-terminus of the zebrafish BMP6 propeptide,and the position and sequence of the cut points have been determined.By comparing the cut point sequences,we found that the first cut point in the zebrafish BMP6 propeptide is the same as the cut point sequence of the human BMP6 propeptide(herein referred to as C1),and the second cut point of the zebrafish BMP6 propeptide is Its unique(referred to as C2 in this article).Through protein profile analysis,we identified the proteins SKP1 and BMP5 that interact with zebrafish BMP6 propeptide for the first time.The GST-pull down experiment proved that SKP1 and BMP5 interact with each other through the sequence of the C2 cut point in the zebrafish BMP6 propeptide.By knocking down SKP1 to explore its function,we found that the bone differentiation-promoting activity of mature BMP6 protein depends on the cleavage regulation of SKP1.By knocking down BMP5 to explore its function,we found that the osteogenic differentiation activity of zebrafish BMP6 depends on BMP5.In addition,based on the reported role of the BMP family in the development of cancer and the maintenance of iron homeostasis,we explored the relationship between human BMP6 propeptide and cancer cell proliferation and iron death.Through overexpression of human BMP6 propeptide and RT-PCR experiments,it is proved that BMP6 propeptide promotes the proliferation of lung cancer cell A549 and osteosarcoma cell MG63 through the Ras signaling pathway;human BMP6 propeptide significantly up-regulates the expression of HAMP,a key regulatory gene of iron metabolism,The expression of iron death-related genes had no significant effect.