1
|
Hu P, Luo BH. Integrin αv
β8
Adopts a High Affinity State for Soluble Ligands Under Physiological Conditions. J Cell Biochem 2017; 118:2044-2052. [DOI: 10.1002/jcb.25780] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Accepted: 11/01/2016] [Indexed: 11/12/2022]
Affiliation(s)
- Ping Hu
- Department of Biological Sciences; Louisiana State University; Baton Rouge Louisiana
| | - Bing-Hao Luo
- Department of Biological Sciences; Louisiana State University; Baton Rouge Louisiana
| |
Collapse
|
2
|
Hu D, Li K, Xie Y, Pan H, Zhao J, Huang L, Zheng X. The combined effects of nanotopography and Sr ion for enhanced osteogenic activity of bone marrow mesenchymal stem cells (BMSCs). J Biomater Appl 2017; 31:1135-1147. [DOI: 10.1177/0885328217692140] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Both surface topography and chemistry have a significant influence on the biological performance of orthopedic implant coatings. In our study, a surface modification strategy embodying bioactive trace element incorporation and nanotopography construction was employed to enhance the osteogenic activity of calcium silicate (Ca-Si) coatings. We developed strontium-loaded nanolayer on plasma sprayed Ca-Si (CS) coating via hydrothermal treatment which was denoted as Sr-NT-CS. The original CS coating and the CS coating modified with similar nanotopography (NT-CS) were studied in parallel. We investigated the cellular effects of surface topography and released Sr ion on the adhesion, proliferation, differentiation, and mineralization of BMSCs and the associated molecular mechanisms. The results indicated that the nanotopography activated integrin β1, promoted the spread of BMSCs into a polygonal osteoblastic shape, and induced higher levels of collagen secretion. The Sr incorporation stimulated osteogenic differentiation and mineralization as indicated by the increases in ALP activity and mineralized nodules formation. The examination of gene expressions revealed that Sr ion exerted the effects by interacting with extracellular calcium sensitive receptor (CaSR), and combined with the nanotopographical cue for the up-regulation of osteogenic master transcription factor Runx2. The promoted Runx2 subsequently affected osteoblast (OB) marker genes (BMP-2, BSP, OPN, and OCN), thus driving BMSCs to differentiate into OBs. Moreover, the Sr incorporation inhibited osteoclastogenesis, as indicated by the down-regulation of interleukin-6 (IL-6) and the inhibition of RANKL/RANK system. Those results suggested that our developed Sr-NT-CS coating have combined the effects of nanotopography and Sr ion for enhanced osteogenic activity of BMSCs.
Collapse
Affiliation(s)
- Dandan Hu
- Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, China; University of Chinese Academy of Sciences, Beijing, China
| | - Kai Li
- Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, China; University of Chinese Academy of Sciences, Beijing, China
| | - Youtao Xie
- Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, China; University of Chinese Academy of Sciences, Beijing, China
| | - Houhua Pan
- Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, China; University of Chinese Academy of Sciences, Beijing, China
| | - Jun Zhao
- Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, China; University of Chinese Academy of Sciences, Beijing, China
| | - Liping Huang
- Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, China; University of Chinese Academy of Sciences, Beijing, China
| | - Xuebin Zheng
- Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, China; University of Chinese Academy of Sciences, Beijing, China
| |
Collapse
|
3
|
Xiang B, Liu Y, Xie L, Zhao Q, Zhang L, Gan X, Yu H. The osteoclasts attach to the bone surface where the extracellular calcium concentration decreases. Cell Biochem Biophys 2016; 74:553-558. [PMID: 27718044 DOI: 10.1007/s12013-016-0757-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 08/12/2016] [Indexed: 02/05/2023]
Abstract
Osteoclasts demineralize and resorb bone once they attach to its surface. However, it's still unclear how the osteoclasts choose the specific sites for their attachments. It is postulated in this article that the decreased extracellular free ionized calcium concentration (Ca2+[e]) can provide a microenvironment for osteoclasts to recognize and then initiate the attachment process. The osteoclasts initially attach to the bone surface via integrating its integrin αvβ3 and RGD containing ligands in bone matrix. Through the interaction with RGD-containing ligand, the integrin αvβ3 forms carboxylate oxygen noncovalent, which is further stabilized by accompanied electrostatic interaction between the Ca2+ and the β3 subunit. There are two types of cation-binding sites on the β3 subunit: the high affinity Ca2+ binding site ("LC" site) that activates the osteoclasts by promoting the combination; the low affinity Ca2+ binding site ("I" site, also named ADMIDAS) that deactivates the osteoclasts by dissociating the combination and it can override the "LC" site's positive effect on osteoclasts when necessary. Normally the Ca2+ concentration of bone extracellular fluid is maintained within a normal range by osteocytes, keeping the "I" sites activated. When the osteocytes' function stalls and the ambient Ca2+ concentration falls below the affinity discrimination threshold between the "I" site and the "LC" site, the "LC" site's promoting function starts to out compete the "I" site in its inhibitory effect, in which case the inactive integrin αvβ3 turns into an extended active form and the osteoclasts start to attach, signifying the initiation of bone resorption.
Collapse
Affiliation(s)
- Bilu Xiang
- The State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Chengdu, China
| | - Yang Liu
- The State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Chengdu, China
| | - Lu Xie
- The State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Chengdu, China
| | - Qian Zhao
- The State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Chengdu, China
| | - Ling Zhang
- The State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Chengdu, China
| | - Xueqi Gan
- The State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Chengdu, China
| | - Haiyang Yu
- The State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Chengdu, China.
| |
Collapse
|
4
|
Abstract
During the past decade, advanced techniques in structural biology have provided atomic level information on the platelet integrin αIIbβ3 activation mechanism that results in it adopting a high-affinity ligand-binding conformation(s). This review focuses on advances in imaging intact αIIbβ3 in a lipid bilayer in the absence of detergent and new structural insights into the changes in the ligand-binding pocket with receptor activation and ligand binding. It concludes with descriptions of novel therapeutic αIIbβ3 antagonists being developed based on an advanced knowledge of the receptor's structure.
Collapse
Affiliation(s)
- B S Coller
- Rockefeller University, New York, NY, USA
| |
Collapse
|
5
|
Disruption of integrin-fibronectin complexes by allosteric but not ligand-mimetic inhibitors. Biochem J 2015; 464:301-13. [PMID: 25333419 DOI: 10.1042/bj20141047] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Failure of Arg-Gly-Asp (RGD)-based inhibitors to reverse integrin-ligand binding has been reported, but the prevalence of this phenomenon among integrin heterodimers is currently unknown. In the present study we have investigated the interaction of four different RGD-binding integrins (α5β1, αVβ1, αVβ3 and αVβ6) with fibronectin (FN) using surface plasmon resonance. The ability of inhibitors to reverse ligand binding was assessed by their capacity to increase the dissociation rate of pre-formed integrin-FN complexes. For all four receptors we showed that RGD-based inhibitors (such as cilengitide) were completely unable to increase the dissociation rate. Formation of the non-reversible state occurred very rapidly and did not rely on the time-dependent formation of a high-affinity state of the integrin, or the integrin leg regions. In contrast with RGD-based inhibitors, Ca2+ (but not Mg2+) was able to greatly increase the dissociation rate of integrin-FN complexes, with a half-maximal response at ~0.4 mM Ca2+ for αVβ3-FN. The effect of Ca2+ was overcome by co-addition of Mn2+, but not Mg2+. A stimulatory anti-β1 monoclonal antibody (mAb) abrogated the effect of Ca2+ on α5β1-FN complexes; conversely, a function-blocking mAb mimicked the effect of Ca2+. These results imply that Ca2+ acts allosterically, probably through binding to the adjacent metal-ion-dependent adhesion site (ADMIDAS), and that the α1 helix in the β subunit I domain is the key element affected by allosteric modulators. The data suggest an explanation for the limited clinical efficacy of RGD-based integrin antagonists, and we propose that allosteric antagonists could prove to be of greater therapeutic benefit.
Collapse
|
6
|
Liu J, Fu T, Peng B, Sun H, Chu H, Li G, Chen J. The hydrophobic contacts between the center of the βI domain and the α1/α7 helices are crucial for the low-affinity state of integrin α4 β7. FEBS J 2014; 281:2915-26. [PMID: 24802248 DOI: 10.1111/febs.12829] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Revised: 04/21/2014] [Accepted: 05/01/2014] [Indexed: 11/28/2022]
Abstract
Integrin α4 β7 mediates both rolling and firm adhesion of lymphocytes by modulating its affinity to the ligand: mucosal addressin cell adhesion molecule-1 (MAdCAM-1). Integrin activation is associated with allosteric reshaping in the β subunit I (βI) domain. A prominently conformational change comprises displacement of the α1 and α7 helices in the βI domain, suggesting that the location of these helices is important for the change in integrin affinity. In the present study, we report that the hydrophobic contacts between the center of the β7 I domain and the α1/α7 helices play critical roles in keeping α4 β7 in a low-affinity state. Using molecular dynamics simulation, we identified nine hydrophobic residues that might be involved in the critical hydrophobic contacts maintaining integrin in a low-affinity state. Integrin β7 I domain exhibited a lower binding free energy for ligand after disrupting these hydrophobic contacts by substituting the hydrophobic residues with Ala. Moreover, these α4 β7 mutants not only showed high-affinity binding to soluble MAdCAM-1, but also demonstrated firm cell adhesion to immobilized MAdCAM-1 in shear flow and enhanced the strength of the α4 β7 -MAdCAM-1 interaction. Disruption of the hydrophobic contacts also induced the active conformation of α4 β7 . Thus, the findings obtained in the present study reveal an important structural basis for the low-affinity state of integrin.
Collapse
Affiliation(s)
- Jie Liu
- State Key Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, China
| | | | | | | | | | | | | |
Collapse
|
7
|
Raborn J, Fu T, Wu X, Xiu Z, Li G, Luo BH. Variation in one residue associated with the metal ion-dependent adhesion site regulates αIIbβ3 integrin ligand binding affinity. PLoS One 2013; 8:e76793. [PMID: 24116162 PMCID: PMC3792891 DOI: 10.1371/journal.pone.0076793] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Accepted: 08/29/2013] [Indexed: 01/06/2023] Open
Abstract
The Asp of the RGD motif of the ligand coordinates with the β I domain metal ion dependent adhesion site (MIDAS) divalent cation, emphasizing the importance of the MIDAS in ligand binding. There appears to be two distinct groups of integrins that differ in their ligand binding affinity and adhesion ability. These differences may be due to a specific residue associated with the MIDAS, particularly the β3 residue Ala252 and corresponding Ala in the β1 integrin compared to the analogous Asp residue in the β2 and β7 integrins. Interestingly, mutations in the adjacent to MIDAS (ADMIDAS) of integrins α4β7 and αLβ2 increased the binding and adhesion abilities compared to the wild-type, while the same mutations in the α2β1, α5β1, αVβ3, and αIIbβ3 integrins demonstrated decreased ligand binding and adhesion. We introduced a mutation in the αIIbβ3 to convert this MIDAS associated Ala252 to Asp. By combination of this mutant with mutations of one or two ADMIDAS residues, we studied the effects of this residue on ligand binding and adhesion. Then, we performed molecular dynamics simulations on the wild-type and mutant αIIbβ3 integrin β I domains, and investigated the dynamics of metal ion binding sites in different integrin-RGD complexes. We found that the tendency of calculated binding free energies was in excellent agreement with the experimental results, suggesting that the variation in this MIDAS associated residue accounts for the differences in ligand binding and adhesion among different integrins, and it accounts for the conflicting results of ADMIDAS mutations within different integrins. This study sheds more light on the role of the MIDAS associated residue pertaining to ligand binding and adhesion and suggests that this residue may play a pivotal role in integrin-mediated cell rolling and firm adhesion.
Collapse
Affiliation(s)
- Joel Raborn
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, United States of America
- University of Alabama at Birmingham School of Medicine, Birmingham, Alabama, United States of America
| | - Ting Fu
- Laboratory of Molecular Modeling and Design, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, PR China
- Department of Bioscience and Biotechnology, Dalian University of Technology, Dalian, PR China
- Graduate University of the Chinese Academy of Sciences, Beijing, P. R. China
| | - Xue Wu
- Laboratory of Molecular Modeling and Design, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, PR China
- Department of Bioscience and Biotechnology, Dalian University of Technology, Dalian, PR China
| | - Zhilong Xiu
- Department of Bioscience and Biotechnology, Dalian University of Technology, Dalian, PR China
| | - Guohui Li
- Laboratory of Molecular Modeling and Design, State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, PR China
- * E-mail: (GL); (BL)
| | - Bing-Hao Luo
- Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, United States of America
- * E-mail: (GL); (BL)
| |
Collapse
|
8
|
Cam A, Sivaguru M, Gonzalez de Mejia E. Endocytic mechanism of internalization of dietary peptide lunasin into macrophages in inflammatory condition associated with cardiovascular disease. PLoS One 2013; 8:e72115. [PMID: 24039740 PMCID: PMC3764169 DOI: 10.1371/journal.pone.0072115] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2013] [Accepted: 07/03/2013] [Indexed: 12/25/2022] Open
Abstract
Cardiovascular disease (CVD) is the leading cause of death in the United States. Diet influences risk factors associated with CVD and atherosclerosis, a major vascular disease that arises from inflammation. Lunasin, a peptide derived from plant foods such as soybeans, contains a unique Arg-Gly-Asp cell-adhesion motif and inhibits the pathways involved in the inflammatory cascade. The objective was to determine the mechanism by which lunasin is internalized into human THP-1 macrophages, investigate the expression of endocytic membrane proteins in inflammatory conditions and to identify the pathways involved. While lipopolysaccharide (10 nM), vitronectin (130 nM) and a combination of these two molecules enhanced lunasin uptake and increased basal αVβ3 integrin expression, lunasin reduced αVβ3 expression by 25.5, 26.8 and 49.2%, respectively. The pretreatment of cells with brefeldin A (71 µM), an inhibitor of protein trafficking, inhibited lunasin internalization by up to 99.8%. Lunasin increased caveolin-1 expression by up to 204.8%, but did not modulate clathrin. The pretreatment of macrophages with nystatin (54 µM), an inhibitor of caveolae-dependent endocytosis, reduced lunasin internalization. The presence of amantadine (1 mM) and amiloride (1 mM), inhibitors of clathrin-mediated endocytosis and macropinocytosis, abolished lunasin cell entry. Lunasin elicited a transient reduction in intracellular levels of Ca2+ in LPS-induced macrophages. The results suggest that internalization of lunasin into macrophages is amplified in inflammatory conditions and is primarily mediated by endocytic mechanisms that involve integrin signaling, clathrin-coated structures and macropinosomes. Lunasin may be responsible for attenuation of CVD risk factors by interacting with pathways involved in endocytosis and inflammation.
Collapse
Affiliation(s)
- Anthony Cam
- Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Mayandi Sivaguru
- Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Elvira Gonzalez de Mejia
- Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
- * E-mail:
| |
Collapse
|