1
|
Ghanim M, Relitti N, McManus G, Butini S, Cappelli A, Campiani G, Mok KH, Kelly VP. A non-toxic, reversibly released imaging probe for oral cancer that is derived from natural compounds. Sci Rep 2021; 11:14069. [PMID: 34234213 PMCID: PMC8263592 DOI: 10.1038/s41598-021-93408-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Accepted: 06/24/2021] [Indexed: 02/06/2023] Open
Abstract
CD44 is emerging as an important receptor biomarker for various cancers. Amongst these is oral cancer, where surgical resection remains an essential mode of treatment. Unfortunately, surgery is frequently associated with permanent disfigurement, malnutrition, and functional comorbidities due to the difficultly of tumour removal. Optical imaging agents that can guide tumour tissue identification represent an attractive approach to minimising the impact of surgery. Here, we report the synthesis of a water-soluble fluorescent probe, namely HA-FA-HEG-OE (compound 1), that comprises components originating from natural sources: oleic acid, ferulic acid and hyaluronic acid. Compound 1 was found to be non-toxic, displayed aggregation induced emission and accumulated intracellularly in vesicles in SCC-9 oral squamous cells. The uptake of 1 was fully reversible over time. Internalization of compound 1 occurs through receptor mediated endocytosis; uniquely mediated through the CD44 receptor. Uptake is related to tumorigenic potential, with non-tumorigenic, dysplastic DOK cells and poorly tumorigenic MCF-7 cells showing only low intracellular levels and highlighting the critical role of endocytosis in cancer progression and metastasis. Together, the recognised importance of CD44 as a cancer stem cell marker in oral cancer, and the reversible, non-toxic nature of 1, makes it a promising agent for real time intraoperative imaging.
Collapse
Affiliation(s)
- Magda Ghanim
- School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland
| | - Nicola Relitti
- Department of Biotechnology, Chemistry and Pharmacy, Department of Excellence 2018-2022, University of Siena, 53100, Siena, Italy
| | - Gavin McManus
- School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland
| | - Stefania Butini
- Department of Biotechnology, Chemistry and Pharmacy, Department of Excellence 2018-2022, University of Siena, 53100, Siena, Italy.
| | - Andrea Cappelli
- Department of Biotechnology, Chemistry and Pharmacy, Department of Excellence 2018-2022, University of Siena, 53100, Siena, Italy
| | - Giuseppe Campiani
- Department of Biotechnology, Chemistry and Pharmacy, Department of Excellence 2018-2022, University of Siena, 53100, Siena, Italy
| | - K H Mok
- School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland
| | - Vincent P Kelly
- School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland.
| |
Collapse
|
2
|
α-Lactalbumin, Amazing Calcium-Binding Protein. Biomolecules 2020; 10:biom10091210. [PMID: 32825311 PMCID: PMC7565966 DOI: 10.3390/biom10091210] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 08/14/2020] [Accepted: 08/17/2020] [Indexed: 02/06/2023] Open
Abstract
α-Lactalbumin (α-LA) is a small (Mr 14,200), acidic (pI 4–5), Ca2+-binding protein. α-LA is a regulatory component of lactose synthase enzyme system functioning in the lactating mammary gland. The protein possesses a single strong Ca2+-binding site, which can also bind Mg2+, Mn2+, Na+, K+, and some other metal cations. It contains several distinct Zn2+-binding sites. Physical properties of α-LA strongly depend on the occupation of its metal binding sites by metal ions. In the absence of bound metal ions, α-LA is in the molten globule-like state. The binding of metal ions, and especially of Ca2+, increases stability of α-LA against the action of heat, various denaturing agents and proteases, while the binding of Zn2+ to the Ca2+-loaded protein decreases its stability and causes its aggregation. At pH 2, the protein is in the classical molten globule state. α-LA can associate with membranes at neutral or slightly acidic pH at physiological temperatures. Depending on external conditions, α-LA can form amyloid fibrils, amorphous aggregates, nanoparticles, and nanotubes. Some of these aggregated states of α-LA can be used in practical applications such as drug delivery to tissues and organs. α-LA and some of its fragments possess bactericidal and antiviral activities. Complexes of partially unfolded α-LA with oleic acid are cytotoxic to various tumor and bacterial cells. α-LA in the cytotoxic complexes plays a role of a delivery carrier of cytotoxic fatty acid molecules into tumor and bacterial cells across the cell membrane. Perhaps in the future the complexes of α-LA with oleic acid will be used for development of new anti-cancer drugs.
Collapse
|
3
|
The novel therapeutic potential of bovine α-lactalbumin made lethal to tumour cells (BALMET) and oleic acid in oral squamous cell carcinoma (OSCC). Eur J Cancer Prev 2020; 30:178-187. [PMID: 32694279 DOI: 10.1097/cej.0000000000000617] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
BACKGROUND Since the serendipitous discovery of bovine α-lactalbumin made lethal to tumour cells (BAMLET)/human α-lactalbumin made lethal to tumour cells there has been an increased interest in the ability of the two components, oleic acid and α-lactalbumin, to form anti-cancer complexes. Here we have investigated the in-vitro efficacy of the BAMLET complex in killing oral cancer (OC) cells, determined the active component of the complex and investigated possible biological mechanisms. MATERIALS AND METHODS Two OC cell lines (±p53 mutation) and one dysplastic cell line were used as a model of progressive oral carcinogenesis. We performed cell viability assays with increasing BAMLET concentrations to determine the cytotoxic potential of the complex. We further analysed the individual components to determine their respective cytotoxicities. siRNA knockdown of p53 was used to determine its functional role in mediating sensitivity to BAMLET. Cell death mechanisms were investigated by flow cytometry, confocal microscopy and the lactate dehydrogenase assay. RESULTS Our results show that BAMLET is cytotoxic to the OC and dysplastic cell lines in a time and dose-dependent manner. The cytotoxic component was found to be oleic acid, which, can induce cytotoxicity even when not in complex. Our results indicate that the mechanism of cytotoxicity occurs through multiple simultaneous events including cell cycle arrest, autophagy like processes with a minor involvement of necrosis. CONCLUSION Deciphering the mechanism of cytotoxicity will aid treatment modalities for OC. This study highlights the potential of BAMLET as a novel therapeutic strategy in oral dysplastic and cancerous cells.
Collapse
|
4
|
El-Fakharany EM, Redwan EM. Protein-lipid complexes: molecular structure, current scenarios and mechanisms of cytotoxicity. RSC Adv 2019; 9:36890-36906. [PMID: 35539089 PMCID: PMC9075609 DOI: 10.1039/c9ra07127j] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2019] [Accepted: 10/21/2019] [Indexed: 02/04/2023] Open
Abstract
Some natural proteins can be complexed with oleic acid (OA) to form an active protein-lipid formulation that can induce tumor-selective apoptosis. The first explored protein was human milk α-lactalbumin (α-LA), called HAMLET when composed with OA in antitumor form. Several groups have prepared active protein-lipid complexes using a variety of approaches, all of which depend on target protein destabilization or direct OA-protein incubation to alter pH to acid or alkaline condition. In addition to performing vital roles in inflammatory processes and immune responses, fatty acids can disturb different metabolic pathways and cellular signals. Therefore, the tumoricidal action of these complexes is related to OA rather than the protein that keeps OA in solution and acts as a vehicle for transferring OA molecules to tumor cells. However, other studies have suggested that the antitumor efficacy of these complexes was exerted by both protein and OA together. The potential is not limited to the anti-tumor activity of protein-lipid complexes but extends to other functions such as bactericidal activity. The protein shell enhances the solubility and stability of the bound fatty acid. These protein-lipid complexes are promising candidates for fighting various cancer types and managing bacterial and viral infections.
Collapse
Affiliation(s)
- Esmail M El-Fakharany
- Protein Research Department, Genetic Engineering and Biotechnology Research Institute, City for Scientific Research and Technology Applications (SRTA-City) New Borg EL-Arab 21934 Alexandria Egypt
| | - Elrashdy M Redwan
- Protein Research Department, Genetic Engineering and Biotechnology Research Institute, City for Scientific Research and Technology Applications (SRTA-City) New Borg EL-Arab 21934 Alexandria Egypt
- Department of Biological Sciences, Faculty of Sciences, King Abdulaziz University P. O. Box 80203 Jeddah Saudi Arabia
| |
Collapse
|
5
|
Abstract
Oleic acid (OA) is a monounsaturated fatty acid that upon binding to milk proteins, such as α-lactalbumin and lactoferrin, forms potent complexes, which exert selective anti-tumor activity against malignant cells but are nontoxic for healthy normal cells. We showed that the interaction of OA with albumins isolated from human, bovine, and camel milk results in the formation of complexes with high antitumor activity against Caco-2, HepG-2, PC-3, and MCF-7 tumor cells. The antitumor effect of the complexes is mostly due to the action of oleic acid, similar to the case of OA complexes with other proteins. Viability of tumor cells is inhibited by the albumin-OA complexes in a dose dependent manner, as evaluated by the MTT assay. Strong induction of apoptosis in tumor cells after their treatment with the complexes was monitored by flow cytometry, cell cycle analysis, nuclear staining, and DNA fragmentation methods. The complex of camel albumin with OA displayed the most pronounced anti-tumor effects in comparison with the complexes of OA with human and bovine albumins. Therefore, these results suggest that albumins have the potential to be used as efficient and low cost means of tumor treatment.
Collapse
|
6
|
Uversky VN, El-Fakharany EM, Abu-Serie MM, Almehdar HA, Redwan EM. Divergent Anticancer Activity of Free and Formulated Camel Milk α-Lactalbumin. Cancer Invest 2017; 35:610-623. [PMID: 28949782 DOI: 10.1080/07357907.2017.1373783] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Alpha-lactalbumin (α-LA), a small milk calcium-binding globular protein, is known to possess noticeable anticancer activity, which is determined by the ability of this protein to form complexes with oleic acid (OA). To date, in addition to human and bovine α-LA, the ability to form such anti-tumor complexes with OA was described for goat and camel α-LA. Although the mechanisms of the anticancer activity of human and bovine α-LA are already well-studied, little is currently known about the anticancer action of this camel protein. The goal of this study was to fill this gap and to analyze the anticancer and pro-apoptotic activities of camel α-LA in its free form (α-cLA) and as an OA-containing complex (OA-α-cLA) using four human cancer cell lines, including Caco-2 colon cancer cells, PC-3 prostate cancer cells, HepG-2 hepatoma cells, and MCF-7 breast cancer cells as targets. The anti-tumor activities of OA-α-cLA and α-cLA were analyzed using MTT test, annexin/PI staining, cell cycle analysis, nuclear staining, and tyrosine kinase (TK) inhibition methods. We show here that the OA-α-cLA complex does not affect normal cells but has noticeable anti-cancer activity, especially against MCF-7 cells, thus boosting the anticancer activity of α-cLA and improving the selectivity of OA. The OA-α-cLA complex mediated cancer cell death via selective induction of apoptosis and cell-cycle arrest at lower IC50 than that of free α-cLA by more than two folds. However, OA induced apoptosis at higher extent than OA-α-cLA and α-cLA. OA also caused unselective apoptosis-dependent cell death in both normal and cancer cells to a similar degree. The apoptosis and cell-cycle arresting effect of OA-α-cLA may be attributed to the TK inhibition activity of OA. Therefore, OA-α-cLA serves as efficient anticancer complex with two functional components, α-cLA and OA, possessing different activities. This study declared the effectiveness of OA-α-cLA complex as a promising entity with anticancer activity, and these formulated OA-camel protein complexes constitute an auspicious approach for cancer remedy, particularly for breast cancer.
Collapse
Affiliation(s)
- Vladimir N Uversky
- a Department of Biological Sciences, Faculty of Sciences , King Abdulaziz University , Jeddah , Saudi Arabia.,b Institute for Biological Instrumentation of the Russian Academy of Sciences , Pushchino , Moscow region , Russia.,c Department of Molecular Medicine and USF Health Byrd Alzheimer's Research Institute , Morsani College of Medicine, University of South Florida , Tampa , FL , USA
| | - Esmail M El-Fakharany
- d Therapeutic and Protective Proteins Laboratory, Protein Research Department, Medical Biotechnology Department, Genetic Engineering and Biotechnology Research Institute , City for Scientific Research and Technology Applications (SRTA-City) , Alexandria , Egypt
| | - Marwa M Abu-Serie
- e Medical Biotechnology Department , Genetic Engineering and Biotechnology Research Institute, City for Scientific Research and Technology Applications (SRTA-City) , Alexandria , Egypt
| | - Hussein A Almehdar
- a Department of Biological Sciences, Faculty of Sciences , King Abdulaziz University , Jeddah , Saudi Arabia
| | - Elrashdy M Redwan
- a Department of Biological Sciences, Faculty of Sciences , King Abdulaziz University , Jeddah , Saudi Arabia.,d Therapeutic and Protective Proteins Laboratory, Protein Research Department, Medical Biotechnology Department, Genetic Engineering and Biotechnology Research Institute , City for Scientific Research and Technology Applications (SRTA-City) , Alexandria , Egypt
| |
Collapse
|
7
|
Kim KH, Yun S, Mok KH, Lee EK. Thermodynamic analysis of ANS binding to partially unfolded α-lactalbumin: correlation of endothermic to exothermic changeover with formation of authentic molten globules. J Mol Recognit 2016; 29:446-51. [DOI: 10.1002/jmr.2543] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2015] [Revised: 02/22/2016] [Accepted: 03/02/2016] [Indexed: 11/11/2022]
Affiliation(s)
- Ki Hyung Kim
- Department of Bionano Engineering; Hanyang University - ERICA; Ansan Korea
| | - Soi Yun
- Department of Bionano Engineering; Hanyang University - ERICA; Ansan Korea
| | - K. H. Mok
- Trinity Biomedical Sciences Institute (TBSI); School of Immunology and Biochemistry; Dublin 2 Ireland
- Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN); Trinity College, The University of Dublin; Dublin 2 Ireland
| | - E. K. Lee
- Department of Bionano Engineering; Hanyang University - ERICA; Ansan Korea
| |
Collapse
|
8
|
Stegmayr BG. New insight in impaired binding capacity for albumin in uraemic patients. Acta Physiol (Oxf) 2015; 215:5-8. [PMID: 26123668 DOI: 10.1111/apha.12546] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- B. G. Stegmayr
- Department of Public Health and Clinical Medicine; University of Umea; Umea Sweden
| |
Collapse
|
9
|
Harte NP, Klyubin I, McCarthy EK, Min S, Garrahy SA, Xie Y, Davey GP, Boland JJ, Rowan MJ, Mok KH. Amyloid Oligomers and Mature Fibrils Prepared from an Innocuous Protein Cause Diverging Cellular Death Mechanisms. J Biol Chem 2015. [PMID: 26221033 DOI: 10.1074/jbc.m115.676072] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Despite significant advances, the molecular identity of the cytotoxic species populated during in vivo amyloid formation crucial for the understanding of neurodegenerative disorders is yet to be revealed. In this study lysozyme prefibrillar oligomers and fibrils in both mature and sonicated states have been isolated through an optimized ultrafiltration/ultracentrifugation method and characterized with various optical spectroscopic techniques, atomic force microscopy, and transmission electron microscopy. We examined their level and mode of toxicity on rat pheochromocytoma (PC12) cells in both differentiated and undifferentiated states. We find that oligomers and fibrils display cytotoxic capabilities toward cultured cells in vitro, with oligomers producing elevated levels of cellular injury toward undifferentiated PC12 cells (PC12(undiff)). Furthermore, dual flow cytometry staining experiments demonstrate that the oligomers and mature fibrils induce divergent cellular death pathways (apoptosis and secondary necrosis, respectively) in these PC12 cells. We have also shown that oligomers but not sonicated mature fibrils inhibit hippocampal long term potentiation, a form of synaptic plasticity implicated in learning and memory, in vivo. We conclude that our in vitro and in vivo findings confer a level of resistance toward amyloid fibrils, and that the PC 12-based comparative cytotoxicity assay can provide insights into toxicity differences between differently aggregated protein species.
Collapse
Affiliation(s)
- Níal P Harte
- Trinity Biomedical Sciences Institute (TBSI), School of Biochemistry and Immunology, Trinity College Dublin, the University of Dublin, Dublin 2, Ireland
| | - Igor Klyubin
- Department of Pharmacology and Therapeutics, Trinity College Institute of Neuroscience (TCIN), Trinity College Dublin, the University of Dublin, Dublin 2, Ireland
| | - Eoin K McCarthy
- School of Chemistry, Trinity College Dublin, the University of Dublin, Dublin 2, Ireland; Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, the University of Dublin, Dublin 2, Ireland
| | - Soyoung Min
- Trinity Biomedical Sciences Institute (TBSI), School of Biochemistry and Immunology, Trinity College Dublin, the University of Dublin, Dublin 2, Ireland
| | - Sarah Ann Garrahy
- TCIN, Trinity College Dublin, the University of Dublin, Dublin 2, Ireland
| | - Yongjing Xie
- Trinity Biomedical Sciences Institute (TBSI), School of Biochemistry and Immunology, Trinity College Dublin, the University of Dublin, Dublin 2, Ireland
| | - Gavin P Davey
- Trinity Biomedical Sciences Institute (TBSI), School of Biochemistry and Immunology, Trinity College Dublin, the University of Dublin, Dublin 2, Ireland; TCIN, Trinity College Dublin, the University of Dublin, Dublin 2, Ireland
| | - John J Boland
- School of Chemistry, Trinity College Dublin, the University of Dublin, Dublin 2, Ireland; Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, the University of Dublin, Dublin 2, Ireland
| | - Michael J Rowan
- Department of Pharmacology and Therapeutics, Trinity College Institute of Neuroscience (TCIN), Trinity College Dublin, the University of Dublin, Dublin 2, Ireland
| | - K Hun Mok
- Trinity Biomedical Sciences Institute (TBSI), School of Biochemistry and Immunology, Trinity College Dublin, the University of Dublin, Dublin 2, Ireland; Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, the University of Dublin, Dublin 2, Ireland.
| |
Collapse
|
10
|
Formation of cytotoxic α-lactalbumin / sodium oleate complexes: Concentration and temperature effects. Int Dairy J 2014. [DOI: 10.1016/j.idairyj.2014.04.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
11
|
Nemashkalova EL, Kazakov AS, Khasanova LM, Permyakov EA, Permyakov SE. Structural characterization of more potent alternatives to HAMLET, a tumoricidal complex of α-lactalbumin and oleic acid. Biochemistry 2013; 52:6286-99. [PMID: 23947814 DOI: 10.1021/bi400643s] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
HAMLET is a complex of human α-lactalbumin (hLA) with oleic acid (OA) that kills various tumor cells and strains of Streptococcus pneumoniae. More potent protein-OA complexes were previously reported for bovine α-lactalbumin (bLA) and β-lactoglobulin (bLG), and pike parvalbumin (pPA), and here we explore their structural features. The concentration dependencies of the tryptophan fluorescence of hLA, bLA, and bLG complexes with OA reveal their disintegration at protein concentrations below the micromolar level. Chemical cross-linking experiments provide evidence that association with OA shifts the distribution of oligomeric forms of hLA, bLA, bLG, and pPA toward higher-order oligomers. This effect is confirmed for bLA and bLG using the dynamic light scattering method, while pPA is shown to associate with OA vesicles. Like hLA binding, OA binding increases the affinity of bLG for small unilamellar dipalmitoylphosphatidylcholine vesicles, while pPA efficiently binds to the vesicles irrespective of OA binding. The association of OA with bLG and pPA increases their α-helix and cross-β-sheet content and resistance to enzymatic proteolysis, which is indicative of OA-induced protein structuring. The lack of excess heat sorption during melting of bLG and pPA in complex with OA and the presence of a cooperative thermal transition at the level of their secondary structure suggest that the OA-bound forms of bLG and pPA lack a fixed tertiary structure but exhibit a continuous thermal transition. Overall, despite marked differences, the HAMLET-like complexes that were studied exhibit a common feature: a tendency toward protein oligomerization. Because OA-induced oligomerization has been reported for other proteins, this phenomenon is inherent to many proteins.
Collapse
Affiliation(s)
- Ekaterina L Nemashkalova
- Institute for Biological Instrumentation of the Russian Academy of Sciences , Pushchino, Moscow region 142290, Russia
| | | | | | | | | |
Collapse
|
12
|
The biological activities of protein/oleic acid complexes reside in the fatty acid. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2013; 1834:1125-43. [DOI: 10.1016/j.bbapap.2013.02.041] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Revised: 02/18/2013] [Accepted: 02/20/2013] [Indexed: 12/12/2022]
|
13
|
Brinkmann CR, Thiel S, Otzen DE. Protein-fatty acid complexes: biochemistry, biophysics and function. FEBS J 2013; 280:1733-49. [DOI: 10.1111/febs.12204] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Revised: 11/29/2012] [Accepted: 02/12/2013] [Indexed: 02/01/2023]
Affiliation(s)
| | - Steffen Thiel
- Department of Biomedicine, Faculty of Health Sciences; Aarhus University; Denmark
| | - Daniel E. Otzen
- Interdisciplinary Nanoscience Centre (iNANO), Centre for Insoluble Protein Structures (inSPIN), Department of Molecular Biology and Genetics; Aarhus University; Denmark
| |
Collapse
|
14
|
Xie Y, Min S, Harte NP, Kirk H, O'Brien JE, Voorheis HP, Svanborg C, Hun Mok K. Electrostatic interactions play an essential role in the binding of oleic acid with α-lactalbumin in the HAMLET-like complex: a study using charge-specific chemical modifications. Proteins 2012; 81:1-17. [PMID: 22777854 DOI: 10.1002/prot.24141] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Revised: 06/15/2012] [Accepted: 06/27/2012] [Indexed: 11/12/2022]
Abstract
Human α-lactalbumin made lethal to tumor cells (HAMLET) and its analogs are partially unfolded protein-oleic acid (OA) complexes that exhibit selective tumoricidal activity normally absent in the native protein itself. To understand the nature of the interaction between protein and OA moieties, charge-specific chemical modifications of lysine side chains involving citraconylation, acetylation, and guanidination were employed and the biophysical and biological properties were probed. Upon converting the original positively-charged lysine residues to negatively-charged citraconyl or neutral acetyl groups, the binding of OA to protein was eliminated, as were any cytotoxic activities towards osteosarcoma cells. Retention of the positive charges by converting lysine residues to homoarginine groups (guanidination); however, yielded unchanged binding of OA to protein and identical tumoricidal activity to that displayed by the wild-type α-lactalbumin-oleic acid complex. With the addition of OA, the wild-type and guanidinated α-lactalbumin proteins underwent substantial conformational changes, such as partial unfolding, loss of tertiary structure, but retention of secondary structure. In contrast, no significant conformational changes were observed in the citraconylated and acetylated α-lactalbumins, most likely because of the absence of OA binding. These results suggest that electrostatic interactions between the positively-charged basic groups on α-lactalbumin and the negatively-charged carboxylate groups on OA molecules play an essential role in the binding of OA to α-lactalbumin and that these interactions appear to be as important as hydrophobic interactions.
Collapse
Affiliation(s)
- Yongjing Xie
- Trinity Biomedical Sciences Institute-TBSI, School of Biochemistry and Immunology, Trinity College Dublin, Dublin 2, Ireland
| | | | | | | | | | | | | | | |
Collapse
|