Modulation of Src Activity by Low Molecular Weight Protein Tyrosine Phosphatase During Osteoblast Differentiation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Background: Src kinase plays a critical role in bone metabolism, particularly in osteoclasts. However, the ability of Src kinase to modulate the activity of other bone cells is less well understood. In this work, we examined the expression and activity of Src and low molecular weight protein tyrosine phosphatase (LMWPTP) during osteoblast differentiation and assessed the modulation of Src kinase by LMWPTP. Methods: Differentiation of MC3T3-E1 pre-osteoblasts was induced by incubation with ascorbic acid and beta-glycerophosphate for up to 28 days. Src phosphorylation and LMWPTP expression were analyzed by immunoblotting. Src dephosphorylation in vitro was assessed by incubating immunoprecipitated Src with LMWPTP followed by assay of the residual Src activity using Sam68 as substrate. The importance of LMWPTP in Src dephosphorylation was confirmed by silencing pre-osteoblasts with siRNA-LMWPTP and then assessing Src phosphorylation. Results: Pre-osteoblast differentiation was accompanied by a decrease in phosphorylation of the activator site of Src and an increase in phosphorylation of the inhibitory site. The expression of total Src was unaltered, indicating that post-translational modifications play a pivotal role in Src function. LMWPTP expression was higher in periods when the activator site of Src was dephosphorylated. LMWPTP dephosphorylated pY(527)-Src and pY(416)-Src in vitro, with greater specificity for pY(527) Src. Activation of LMWPTP produced strong activation of Src mediated by fast dephosphorylation of pY(527)-Src, followed by slower deactivation of this kinase via dephosphorylation of pY(416) Src. Conclusion: These results provide new insight into the mechanisms governing the dynamics of Src activity during osteoblast differentiation. A fuller understanding of these mechanisms will improve our knowledge of bone metabolism and of the regulation of Src in other types of cells. Copyright (c) 2008 S. Karger AG, Basel2241795497506Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [04/14906-2

The Src inhibitor dasatinib accelerates the differentiation of human bone marrow-derived mesenchymal stromal cells into osteoblasts

The proto-oncogene Src is an important non-receptor protein tyrosine kinase involved in signaling pathways that control cell adhesion, growth, migration and differentiation. It negatively regulates osteoblast activity, and, as such, its inhibition is a potential means to prevent bone loss. Dasatinib is a new dual Src/Bcr-Abl tyrosine kinase inhibitor initially developed for the treatment of chronic myeloid leukemia. It has also shown promising results in preclinical studies in various solid tumors. However, its effects on the differentiation of human osteoblasts have never been examined.Journal ArticleResearch Support, Non-U.S. Gov'tSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Biological behavior of pre- osteoblasts on natural hydroxyapatite: A study of signaling molecules from attachment to differentiation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Several biomaterials have been widely used in bone regeneration in both orthopedic and oral surgeries. However, it is poorly understood how these biomaterials alter osteoblast phenotype. It prompted us to examine the involvement of signaling proteins during preosteoblast adhesion (attachment), proliferation, and differentiation on natural hydroxyapatite (HA) from bovine bone. Our results indicated that natural HA is able to promote osteoblast adhesion, proliferation, and differentiation. The osteoblast/HA interaction requires phosphorylation of tyrosine residues of focal adhesion kinase, Src, and Paxillin upon integrin activation, which culminates in the control of cofilin phosphorylation (at serine 03) via rac-1 activation. In part, these signaling pathways are responsible for actin-rearrangement, responsible to adapt cell-shape on HA particles. In regarding to osteoblast differentiation, we showed that natural HA favored extracellular matrix remodeling by stimulating matrix metalloproteinase activities and alkaline phosphatase activity. Overall, this study demonstrates that osteoblast response toward bovine bone HA is initially mediated by activation of focal adhesion components, culminating on actin-rearrangement executed by cofilin activation via rac-1. Moreover, bovine bone HA provided an excellent microenvironment for osteoblast activity, since adhesion to differentiation. (C) 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 97A: 193-200, 2011.97A2193200Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [08/53003-9

A simple method for enhancing cell adhesion to hydroxyapatite surface

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Objectives Increase cell adhesion on hydroxyapatite (HA) surface, in a simple, fast and inexpensive way. Material and methods Hydroxyapatite powder was immersed into deionized water for 15 days, dried and pressed into discs. On those discs, pre-osteoblasts cells were cultured for 30 min and 24 h, and adhesion was analyzed by MTT reduction. Results The results show that HA treatment in equilibrium with water drastically increases cell adhesion when compared with cultures on HA with no treatment. The results also show that one essential factor required for a complete modification of HA is the amount of time of immersion in water. Conclusions The work presented here suggests a new, simple and effective method to improve the success of different implants. The method is simple, inexpensive and can be used in the daily routine of different contexts where implants are used, from bone substitution to dental procedures. To cite this article:Bertazzo S, Zambuzzi WF, Campos DDP, Ferreira CV, Bertran CA. A simple method for enhancing cell adhesion to hydroxyapatite surface.Clin. Oral Impl. Res. 21, 2010; 1411-1413.doi: 10.1111/j.1600-0501.2010.01968.x.211214111413Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq