The long term goal of the proposed studies is to understand the mechanisms of cell signaling in the regulation of key cellular functions in skeletal development/disease. In this proposal, we focus on the role of FIP200 (FAK-family Interacting Protein of 200 kDa) in the regulation of osteoblast differentiation. FIP200 was initially identifie as a novel FAK and Pyk2 inhibitor. Recently, FIP200 was identified as an essential component of mammalian autophagy. Despite our knowledge about FIP200 as a key signaling node in both embryogenesis and cancer development, it is unknown to what extent FIP200 regulates bone metabolism. In our preliminary studies, we found: 1. FIP200 conditional knockout in osteoblasts led to a severe osteopenic phenotype;2. Osteoblast differentiation was greatly impaired in FIP200-null primary osteoblast cultures;3. Primary calvarial osteoblasts have active basal and high inductive autophagy activity. However, FIP200 null primary calvarial osteoblasts expressing GFP-LC3 failed to form punctuate membrane structures in response to starvation and rapamycin treatment, indicating that FIP200 null osteoblasts had autophagy deficiency;4. FIP200-null osteoblasts had large ubiquitin-positive aggregates, another indication of defective autophagy in these cells;and 5. Early neonatal FIP200 Osx-CKO mice had significant growth retardation in response to naturally occurring starvation as a result of sudden loss of maternal blood supply. Therefore, we hypothesize that FIP200 regulates bone mass through its regulation on osteoblast autophagy. The overall objective of the proposed project is to determine the molecular mechanisms and signaling pathways by which FIP200 regulates osteoblast function and bone mass using a combination of molecular, cell biological and mouse genetic approaches.
The specific aims of this proposal are:
Aim 1. To determine to what extent FIP200 regulates osteoblast function through its autophagic role.
Aim 2. To elucidate the mechanism by which FIP200 regulates early postnatal bone development.
Aim 3. To determine the role of FIP200 in bone homeostasis in adult mice. Health relevence: As a major public health threat, osteoporosis is present in an estimated 44 million men and women aged 50 and older, which represents 55 percent of the population in that age group in the USA. The proposed study with unique mouse disease model is highly valuable for determining the molecular and cellular mechanisms of pathogenesis of osteoporosis. It will allow us to define a novel bone mass regulation mechanism by autophagy, which is fundamentally important for the development of new therapeutics to treat bone diseases including osteoporosis. 1
Osteoporosis is a condition in which the bones become weak and can break more easily. FIP200 is a newly identified signaling molecule that plays many important roles in different tissue/cell types. This proposed project will elucidate the mechanisms of osteoporotic lesion in a mouse model in which FIP200 is deficient. The pathways and mechanisms identified can be potentially utilized for the future novel treatment of osteoporosis as well as other bone diseases.
|Wei, X; Hu, M; Mishina, Y et al. (2016) Developmental Regulation of the Growth Plate and Cranial Synchondrosis. J Dent Res 95:1221-9|
|Shi, Ce; Iura, Ayaka; Terajima, Masahiko et al. (2016) Deletion of BMP receptor type IB decreased bone mass in association with compromised osteoblastic differentiation of bone marrow mesenchymal progenitors. Sci Rep 6:24256|
|Sun, Chunhui; Yuan, Hebao; Wang, Li et al. (2016) FAK Promotes Osteoblast Progenitor Cell Proliferation and Differentiation by Enhancing Wnt Signaling. J Bone Miner Res :|
|(2016) Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition). Autophagy 12:1-222|
|Sun, Shaogang; Chen, Song; Liu, Fei et al. (2015) Constitutive Activation of mTORC1 in Endothelial Cells Leads to the Development and Progression of Lymphangiosarcoma through VEGF Autocrine Signaling. Cancer Cell 28:758-72|
|Fang, Fang; Sun, Shaogang; Wang, Li et al. (2015) Neural Crest-Specific TSC1 Deletion in Mice Leads to Sclerotic Craniofacial Bone Lesion. J Bone Miner Res 30:1195-205|
|Fang, Fang; Wei, Xiaoxi; Hu, Min et al. (2015) A mouse model of craniofacial bone lesion of tuberous sclerosis complex. Musculoskelet Regen 1:|
|Wang, Li; Mishina, Yuji; Liu, Fei (2015) Osterix-Cre transgene causes craniofacial bone development defect. Calcif Tissue Int 96:129-37|
|Chen, Yongqiang; Wei, Huijun; Liu, Fei et al. (2014) Hyperactivation of mammalian target of rapamycin complex 1 (mTORC1) promotes breast cancer progression through enhancing glucose starvation-induced autophagy and Akt signaling. J Biol Chem 289:1164-73|
|Liu, Fei; Fang, Fang; Yuan, Hebao et al. (2013) Suppression of autophagy by FIP200 deletion leads to osteopenia in mice through the inhibition of osteoblast terminal differentiation. J Bone Miner Res 28:2414-30|
Showing the most recent 10 out of 13 publications