• Therapeutic Targeting of P2X7 After Traumatic Brain Injury

      Kimbler, Donald E.; Department of Neurosurgery (2012-02)
      Traumatic brain injury (TBI) is a leading cause of death and disability worldwide. Cerebral edema, the abnormal accumulation of fluid within the brain parenchyma, contributes to elevated intracranial pressure (ICP) and is a common life-threatening neurological complication following TBI. Unfortunately, neurosurgical approaches to alleviate increased ICP remain controversial and medical therapies are lacking due in part, to the absence of viable drug targets. In the present study, genetic inhibition (P2X7-/- mice) of the purinergic P2X7 receptor attenuated the expression of the pro-inflammatory cytokine, interleukin-iP (IL-ip) and reduced cerebral edema following controlled cortical impact, as compared to wild-type mice. Similarly, the clinically useful P2X7 inhibitor, brilliant blue G (BBG), inhibited the expression of IL-ip, limited edemic development and prevented the development of post-traumatic depression and anxiety. The beneficial effects of BBG were observed following either prophylactic administration via the drinking water for one week prior to injury or via an intravenous bolus administration up to four hours after TBI, suggesting a clinically-implementable therapeutic window. Notably, P2X7 localized within astrocytic end feet and administration of BBG decreased the expression of glial fibrillary acidic protein (GFAP), a reactive astrocyte marker, and reduced the expression of aquaporin-4 (AQP4), an astrocytic water channel that promotes cellular edema. Together, these data implicate P2X7 as a novel therapeutic target to prevent secondary neurological injury after TBI, a finding that warrants further investigation.
    • Therapeutic Targeting of P2X7 after Traumatic Brain Injury

      Kimbler Jr, Donald E; Department of Neuroscience and Regenerative Medicine (Georgia Health Sciences University, 2012-02)
      Traumatic brain injury (TBI) is a leading cause of death and disability worldwide. Cerebral edema, the abnormal accumulation of fluid within the brain parenchyma, contributes to elevated intracranial pressure (ICP) and is a common life-threatening neurological complication following TBI. Unfortunately, neurosurgical approaches to alleviate increased ICP remain controversial and medical therapies are lacking due in part, to the absence of viable drug targets. In the present study, genetic inhibition (P2X7-/- mice) of the purinergic P2x7 receptor attenuated the expression of the pro-inflammatory cytokine, interleukin-I~ (IL-1~) and reduced cerebral edema following controlled cortical impact, as compared to wild-type mice. Similarly, the clinically useful P2X7 inhibitor, brilliant blue G (BBG), inhibited the expression of IL-1~, limited edemic development and prevented the development of post-traumatic depression and anxiety. The beneficial effects of BBG were observed following either prophylactic administration via the drinking water for one week prior to injury or via an intravenous bolus administration up to four hours after TBI, suggesting a clinically-implementable therapeutic window. Notably, P2X7 localized within astrocytic end feet and administration of BBG decreased the expression of glial fibrillary acidic protein (GFAP), a reactive astrocyte marker, and reduced the expression of aquaporin-4 (AQP4), an astrocytic water channel that promotes cellular edema. Together, these data implicate P2X7 as a novel therapeutic target to prevent secondary neurological injury after TBI, a finding that warrants further investigation.
    • This retrospective study attempted to identity differences between student groups occurring before and after the restructuring of the Army occupational therapy assistant (OTA) program. Records of 168 students were reviewed (104 records of students in the pre-restructuring group, 64 in the post-restructuring group). Several areas were examined: (a) demographic data, (b) course attrition rates, (c) performance on level II fieldwork, and (d) national certification exam pass rates. Analyses of demographic data revealed that students in the post-restructuring group were significantly older (p<.OOl) and of higher rank (p<.001) than students in the pre-restructuring group. Analysis using a chi-square test revealed a significant decrease in the attrition rate (p<.001) after the restructuring. At-test revealed that students in the post-restructuring group performed significantly better on their level II fieldwork (p=.030). National certification exam pass rates for the groups could not be determined due to the confidential nature in which scores are reported

      Harrison-Weaver, Sandra; Medical College of Georgia (Augusta University, 1997-03)
      This retrospective study attempted to identity differences between student groups occurring before and after the restructuring of the Army occupational therapy assistant (OTA) program. Records of 168 students were reviewed (104 records of students in the pre-restructuring group, 64 in the post-restructuring group). Several areas were examined: (a) demographic data, (b) course attrition rates, (c) performance on level II fieldwork, and (d) national certification exam pass rates. Analyses of demographic data revealed that students in the post-restructuring group were significantly older (p<.OOl) and of higher rank (p<.001) than students in the pre-restructuring group. Analysis using a chi-square test revealed a significant decrease in the attrition rate (p<.001) after the restructuring. At-test revealed that students in the post-restructuring group performed significantly better on their level II fieldwork (p=.030). National certification exam pass rates for the groups could not be determined due to the confidential nature in which scores are reported
    • Tissue culture study of clinical specimens from an outbreak of rubella-like illness

      Reddick, Rhoda Anne; Department of Cell and Molecular Biology (1968-06)
    • Tissue culture study of clinical specimens from an outbreak of rubella-like illness

      Reddick, Rhoda Anne; Department of Cell and Molecular Biology (1965-06)
    • Tissue metabolism of thyroid hormones in hypothyroid and growth hormone treated hypothyroid mothers, their fetuses and their progenies

      Berdecia-Rodriguez, Joseph; Department of Physiology and Endocrinology (1990-05)
      Studies of Man et al. have shown that the children of hypothyroxinemic women have an .increased rate of mental and .motor retardation. A rat model which presents the ~etabolic and motor defects of these children developed by Hendrich et al. was used for these studies. The metabolism of T4 was studied i~ the progenies of Tx-only and GH-treated Tx dams utilizing a radioimmunoassay for T4 detection and equations based on those of Inglebleek .~d Malvaux. In the above mentioned study, the hypothyroid dams showed an impaired reproductive performance that included lower body weight gain, smaller liter size and greater mortality for their pups. Furthermore, maternal hypothyroidism had a detrimental effect on their offsprings body and tissue weights. The parameters of metabolism for T4 showed that the offsprings of hypothyroid mothers have a clear derangement in the utilization of this hormone at the ages studied (i.e., 5, 30, 60 days of age). The next step in our investigation wa~ to measure the iodothyronine concentrations intracellularly to determine how these J molecules were utilized. We developed a new technique for the extraction of iodothyronines based on HPLC fluorescence. The extracted iodothyronines were derivatized with dansyl chloride and then rap in our chromatographic system. The iodothyronine concentrations ·in the tissues {i.e., brain and liver) and plasma for the progenies of hypothyroid mothers at all ages {i.e,. 22 day, 10, 30, 60 day-olds} were consistently abnormal confirming what we saw with the metabolic studies of T4 done initially. The hypothyroid mothers had iodothyronine concentrations consistently abnormal in all tissues studies. The progenies of hypothyroid mothers appear to suffer an insult that causes a severe impairment in the metabolism of T4. This insult not only affects the metabolism of T4 but also affects the concentrations' of other iodothyronines in liver, brain and plasma
    • Toll-like receptor 2 contributes to cerebrovascular dysfunction and cognitive impairment in diabetes

      Hardigan, Trevor; Department of Physiology (2016-03)
      The risk of cognitive decline in diabetes (Type 1 and Type 2) is significantly greater compared to normoglycemic patients, and the risk of developing dementia in diabetic patients is doubled. The etiology for this is likely multifactorial, but one mechanism that has gained increasing attention is decreased cerebral blood flow (CBF) as a result of cerebrovascular dysfunction. The innate immune system has been shown to play a role in diabetic vascular complications, notably through Toll-like receptor (TLR) stimulated release of proinflammatory cytokines and chemokines that leads to vascular damage. TLR2 has been implicated in the development of diabetic microvascular complications such as nephropathy, and thus we hypothesized that TLR2-mediated cerebrovascular dysfunction leads to decreased CBF and cognitive impairment in diabetes. Vascular TLR2 expression was increased and local TLR2 antagonism improved cerebrovascular function in diabetes. While the anti-hyperglycemic dipeptidylpeptidase-IV (DPP-IV) inhibitor linagliptin prevented TLR2 expression in brain microvascular endothelial cells (BMVEC) when applied locally, chronic in vivo treatment did not decrease vascular smooth muscle TLR2 expression. Treatment with linagliptin restored CBF in diabetes independent of effects on blood glucose levels, and this increase in CBF was correlated with decreased endothelin-1 (ET-1)-mediated vasoconstriction, decreased pathological remodeling, and increased endothelium-dependent relaxation. Knockout of TLR2 conferred protection from impaired CBF in early-stage diabetes and from hyperperfusion in long-term diabetes, prevented the development of endothelium dependent vascular dysfunction in diabetes, created a hyperactive and anxiolytic phenotype, and protected against diabetes induced impairment of long term hippocampal- and prefrontal cortex- mediated fear learning. In conclusion, these findings support the involvement of TLR2 in the pathogenesis of diabetic vascular disease and cognitive impairment.
    • Toll-like receptor 9 contributes to vascular dysfunction in hypertension

      McCarthy, Cameron; Department of Physiology (2016-03)
      Inappropriate immune system activation is common in hypertension; however, the exact mechanisms by which this occurs are not well understood. Innate immune system recognition and response to damage-associated molecular patterns (DAMPs) is becoming an increasingly accepted mechanism. Mitochondrial DNA (mtDNA) is a DAMP that is recognized by Toll-like receptor (TLR)9, and it is elevated in the circulation of spontaneously hypertensive rats (SHR). Therefore, we hypothesized that (1) inhibition of TLR9 in SHR with a TLR9 antagonist (ODN2088) or TLR9 inhibitor (chloroquine) would lower blood pressure and improve vascular function and that (2) treatment of normotensive rats with a TLR9 agonist (ODN2395) would cause vascular dysfunction and increase blood pressure. Both ODN2088 and chloroquine lowered high blood pressure in SHR and treatment with chloroquine also improved cyclooxygenase-dependent endothelial function and prevented the full recruitment of the adaptive immune system in SHR. On the other hand, treatment of normotensive rats with ODN2395 increased blood pressure and rendered their arteries less sensitive to acetylcholine-induced relaxation and more sensitive to norepinephrine-induced contraction. This dysfunctional vasoreactivity was due to cyclooxygenase activation, increased reactive oxygen species generation, and reduced nitric oxide bioavailability. In conclusion, these findings support the involvement of the innate immune system pattern recognition receptor TLR9 in the pathogenesis and maintenance of hypertension. Specifically, circulating mtDNA may activate TLR9 and contribute to high blood pressure and endothelial dysfunction in SHR.
    • Toothbrush abrasion of a novel porcelain esthetic characterization technique

      Chi, Woo Jun Amos; Medical College of Georgia (Augusta University, 2008-07)
    • Toxicity of visible light-cured denture resins

      Barron, Dara Jewell; Department of Oral Biology (1992-04)
      In this study three commercial formulations of visible light-cured (VLC) denture resins have been analyzed. The products used are those suggested for the reline, repair and fabrication of dentures to improve their fit. The biocompatibility of these resins was investigated by measuring RNA and DNA synthesis of oral epithelial cells in vitro. The extent to which oral cells recover from toxic resin exposure, the conversion of monomer into polymer, the presence of inorganic filler, and resin leacha~ility have also been studied. It was shown that VLC denture resins inhibit the synthesis of RNA and· DNA relative to a heat-cured resin control (p~0.05). Although epithelial cells appeared to recover from toxic resin exposure, this recovery was inconsistent among experiments. Infrared spectroscopy illustrated chemical group differences that occurred before and after photo-polymerization. Using these differences, the conversion of monomer into polymer ranged from 77% to 97%. This conversion was significantly affected (p< .003) by the type of curing unit, duration of photo-polymerization, and surface exposed to visible light. Soluble substances in cured and uncured resin products were analogous using HPLC. The range of inorganic filler present was 0-15%. These investigations suggest that visible light-cured denture resins may impair the replication of oral epithelial cells. This effect may be related to the leachability of unpolymerized resin constituents, the presence or absence of filler particles, or polymerization by-products.
    • Transcriptional Coactivator and Oncoprotein CoAA

      Brooks, Yang Sui; Department of Pathology (2008)
      CoAA contains two copies of RNA recognition motifs (RRM) and an intrinsic transactivation domain rich in repetitive tyrosines and glutamines (YxxQ domain). Previously, CoAA has been shown to be a transcriptional coactivator that stimulates transcriptional activation and regulates alternative splicing. A pattern and profile search revealed that the YxxQ domain in CoAA shared significant pattern homology with the oncogenic EWS activation domains (EAD) in TET family proteins, including, TLS/FUS, EWS and TAFII 68. It was further demonstrated that CoAA’s YxxQ domain and EWS’ EAD also shared functional similarities. Based on these findings, this work investigated the aberration of CoAA in cancers and its pathophysiological significance. The results showed that the CoAA gene was amplified in a high percentage of inflammation-related human cancers with recurrent loss of the 5’ regulatory element upstream of its promoter. This genomic aberration resulted in CoAA protein overexpression, which in turn, induced the transformation of NIH3T3 cells. Subsequently, it was shown that the lost 5’ regulatory element could modulate the alternative splicing of the CoAA gene during stem cell differentiation and that the unbalanced expression of CoAA and its splice variant, CoAM could potentially impact the cell differentiation process. To further characterize the regulation of CoAA alternative splicing, two conserved trans-splicing events between CoAA and its downstream RBM4 were identified. These events yield a novel zinc finger- containing coactivator, CoAZ, and a non-coding splice variant, ncCoAZ. Both variants regulated their parental genes’ mRNA expression as well as activities, suggesting a linked control between CoAA and RBM4. Moreover, the expression patterns of CoAA, RBM4 and their trans-splicing variants switched during neural stem cell differentiation, resulting in lineage-specific expression of each variant. Our phylogenetic analysis suggests that mammalian CoAA and RBM4 share a common ancestor with the Drosophila melanogaster gene, Lark. In this regard, the trans-splicing events between CoAA and RBM4 represent a functional regulation preserved during evolution. This study established the connection between CoAA and human cancer and provides evidence for CoAA’s involvement in the regulation of cell differentiation. Moreover, this study is the first to report a functional trans-splicing variant in mammalian cells.
    • Transcriptional coactivator and oncoprotein CoAA

      Brooks, Yang Sui; Medical College of Georgia (Augusta University, 2008-08)
      CoAA contains two coptes of RNA recognition motifs (RRM) at).d an intrinsic transactivation domain rich in repetitive tyrosines and glutamines (YxxQ domain). Previously, CoAA has been shown to be a transcriptional coactivator that stimulates transcriptional activation and regulates alternative splicing. A pattern and profile search revealed that the Y xxQ domain in CoAA shared significant pattern homology with the oncogenic EWS activation domains (BAD) in TBT family proteins, including, TLS/FUS, 1!: EWS and TAFII 68. It was further demonstr~ted that CoAA's YxxQ domain and BWS' BAD also shared functional similarities. Based on these findings, this work investigated the aberration of CoAA in cancers and its pathophysiological significance. The results showed that the CoAA gene was amplified in a high percentage of inflammation-related human cancers with recurrent loss of the 5' regulatory element upstream of its promoter. This genomic aberration resulted in CoAA protein overexpression, which in tum, induced the transformation of NIH3T3 cells. Subsequently, it was shown that the lost 5' regulatory element could modulate the alternative splicing of the CoAA gene during stem cell differentiation and that the unbalanced expression of CoAA and its splice variant, CoAM could potentially impact the cell differentiation process. To further characterize the regulation of CoAA alternative splicing, two conserved trans-splicing events between CoAA and its downstream RBM4 were identified. These events yield a novel zinc finger containing coactivator, CoAZ, and a non-coding splice variant, ncCoAZ. Both variants regulated their parental genes' mRNA expression as well as activities, suggesting a linked control between CoAA and RBM4. Moreover, the expression patterns of CoAA, RBM4 and their trans-splicing variants switched during neural stem cell differentiation, resulting in lineage-specific expression of each variant. Our phylogenetic analysis suggests that mammalian CoAA and RBM4 share a common ancestor with the Drosophila melanogaster gene, Lark. In this regard, the trans-splicing events between CoAA and RBM4 represent a functional regulation preserved during evolution. This study established the connection between CoAA and human cancer and provides evidence for CoAA's involvement in the regulation of cell differentiation. Moreover, this study is the first to report a functional trans-splicing variant in mammalian cells.
    • Transcriptional regulation by TBX2

      Chen, Jung-Ren; Medical College of Georgia (Augusta University, 2001-03)
      Tbx2 is a member of an evolutionarily conserved transcriptional regulatory gene family. Little is. known about th~ molecular mechanisms underlying the function of Tbx2. Because connexin43 ( Cx43) and Tbx2 are both expressed in neural crest derivatives in pharyngeal arches and because the promoter of Cx43 contains· direct repeats ofT (Brachyury) half sites, it is hypothesized that Tbx2 regulates Cx43 and other genes important for neural crest cell functions. TBX2 DNA binding affinity was analyzed by eletrophoretic mobility shift assays. Transcriptional regulation of the Cx43 promoter by Tbx2 was analyzed using reporter constructs. These results suggest that Cx43 is a bona fide target gene of Tbx2 and that Tbx2 negatively regulates Cx43 gene expression by binding to TCACAC sites. Moreover, dye-coupling assays showed that Tbx2 upregulation led to decreased junctional coupling. To identify other genes that may be regulated by Tbx2, a differential gene expression profile was determined using GEMl microarrays. CellSpace knowledgebase was used to perform functional assignments to Tbx2-regulated genes. This analysis indicated that Tbx2 might be involved in different fundamental cell functions. Tbx2 upregulates proliferation genes, downregulates tenascinC, and upregulates nidogen. In conclusion, together with Cx43 repression, Tbx2 may signal neural crest cells to stop migration and start p~oliferation. Gene cluster analysis also suggested a potential role for Tbx2 in osteogenesis. In accord, Tbx2 expression was detected in chondrocytes and osteocytes both in long bone and membranous bones.
    • Transformation from Informal Community Group to Community-Based Health Care Organization: A Case Study of Change

      Hanson, Glenda F; Department of Physiological and Technological Nursing (1996-03)
      The purpose o f this study was to examine the transformations of the organization, AID Atlanta in it’s first ten years to determine how and why decisions were made which lead from an informal community group to the creation of the successful, viable, community-based health care organization. Case study methodology was used to conduct the investigation. Sources o f data included primary and secondary documents, direct observations, and systematic interviewing. The theoretical framework for this study was the theory of dissipative structures, as developed by Prigogine (1976) and others within the fields of biology and chemistry. A number o f social scientists have applied this theory to the study of organizational change and transformation. The theory conceptualizes organizations as open systems that exchange energy with the environment, are self determining, and self organizing. Change is conceived as a normal response to an uncertain and complex environment. The study found that AID Atlanta underwent a series o f changes and transformations which enabled it to grow, survive and remain viable. Forces influencing the organization came from both the internal and external environment, with the most powerful force being the AIDS epidemic. Decisions were made by numerous individuals which served to shape the success o f the organization. The clear and constant mission of the organization was a positive sustaining force, and the development of linkages to the community was a key factor in securing necessary resources. Implications o f the study are that decision makers in community-based health care organizations must expect and prepare for change. Knowledge of the experiences of similar successful organizations may lead the administrator to develop strategies which may serve to promote their own success. Strategies shown to promote viability in this study included an open exchange with the internal and external environments, a willingness to change, the use of resources from external connections, articulation o f a vision based on the mission, knowledgeable and experienced leaders, and a strong foundation and heritage.
    • Transformation from informal community group to community-based health care organization: a case study of change

      Hanson, Glenda F.; Medical College of Georgia (Augusta University, 1996-03)
      The purpose of this study was to examine the transformations of the organization, AID Atlanta in it's first ten years to determine how and why decisions were made which lead from an informal community group to the creation of the successful, viable, community-based health care organization. Case study methodology was used to conduct I the investigation. Sources of data included primary and secondary documents, direct observations, and systematic interviewing. The theoretical framework for this study was the theory of dissipative structures, as developed by Prigogine (1976) and others within the tields of biology and chemistry. A number of social scientists have applied this theory to the study of organizational change and transformation. The theory conceptualizes organizations as open systems that exchange energy with the environment, are ·self determining, and self organizing. Change is conceived as a normal response to an uncertain artd complex environment. The study found that AID Atlanta underwent a series of changes and transformations which enabled it to grow, survive and remain viable. Forces influencing the organization came from both the internal and external environment, with the most powerful force being the AIDS epidemic. Decisions were made by numerous individuals which served to shape the success of the organization. The clear and constant mission of the organization was a positive sustaining force, and the development of linkages to the community was a key factor in securing necessary resources. Implications of the study are that decision makers in community-bas.ed health care organizations must expect and prepare for change. Knowledge of the dxperiences of I similar successful organizations may lead the administrator to develop st~ategies which may serve to promote their own success. Strategies shown to promote viability in this study included an open exchange with the internal and external environments, a willingness to change, the use of resources from external connections, articulation of a vision ba.$ed on the mission, knowledgeable and experienced leaders, .and a strong foundation and heritage.
    • Transformation of neisseria gonorrhoeae with gonococcal and meningo- coccal DNA

      Wood, David Oliver; Department of Cell and Molecular Biology (1975-06)
    • A Transforming Growth Factor From MCG-T14 Mouse Mammary Carcinoma Cells

      Cheng, Charles; Department of Cell and Molecular Biology (1983-04)
      Mitogenic activity was assayed in the harvest fluid concentrates (HFC) from. human· mammary cell.lines ·(T47P, HSO 578T, MDA-157, HBL-100 and BT-20) and a mouse mamamry carcinOinii (MCG-T14) cell line. Data showed that the HFC from four of the human cell lines (T47D,.HSO 578T, MDA-157, and HBL-fOO) and the mouse cell line (MCG-Tl4) were sour.ces of mitogenic activity. The mitogenic activity from the HFC was not due to the action of the serine protease, plasminogen activator. The mitogenic substance was also not a cell degradation product. The HFC from the human mammary carcinoma line BT-20 contained a non-dialyzable inhibitory activity which su~pressed the activities of the mitogerts in fetal bovine serum. Attempts to isolated the mitogenic activity from HFCs proved impractical due to proteolytic breakdown. However, a transforming growth factor (TGF) from acid-ethanol extracts of MCG-T14'mouse mammary carcinoma ' ' cells was isolate~ and·partially characterized. This factor stimulated thymidine uptake in BALB/c 3T3 cells and promoted anchorage-independent growth of NRK-49F cells in soft agar. The mitogenic activity, designated T14-TGF, stimulted thymidine uptake in conflue.nt-quiescent BALB/c 3T3 cells to the same extent as tha,t exhibited by 5% calf serum. T14-TGF was potentiated by EGF in its ability to promote colonial growth of NRK-49F cells. In competition binding assays, T14-TGF and EGF competed for binding to BALB/c 3T3 and A431 cells. However, EGF was a more efficien~ competitor than T14-TGF in all experiments and T14-TGF exhibited only partial inhibition of EGF-binding to A431 cells. This suggests that T14-TGF may have contained subfractions which did not compete for EGF binding sites. Nerve growth factor, fibroblast growth factor, and multiplication stimulating activity did not compete with T14-TGF for binding .. 1 sites .on BALB/c 3T3 cells. In addition, iodinated T14-TGF did not bind to NR6/6 3T3 cells which lack EGF receptors. It was concluded that Tl4-TGF must interact with EGF receptors specifically~ 2 T14-TGF was purified to apparent electrophoretic homogeneity by electroelution from 15% SDS-urea polyacrylamide gelso The factor was basic (pi 8.3), had anapparent moleculaJ; weight of 14,000 and was selectively inactivated by trypsin. In addition, T14-TGF exhibited no proteolytic activity and contained no carbohydrate residues. The biological activity of T14-TGF was resistant to inactivation by acid or heat and· denaturation by guanidine HCl. T14-TGF was completely inactivated by treatment with dithiothreitol which indicated that it required one or more intact disulfide .bridges for activ~ty. A unique characteristic of T14 ... TGF was that this factor bound very strongly to. both DEAE or carboxymethyl f:on excha'Iigers. T14-TGF contained high proportions of basic amino acid residues lys~ne and arginine.
    • Transient Self-Association of Beta2-Adrenergic Receptors

      Lan, Tien-Hung; Department of Pharmacology and Toxicology (2014-03)
      G-protein coupled receptors (GPCRs) constitute the largest family of cell surface receptors. Through binding to ligands such as hormones, peptides, neurotransmitters, or photons, GPCRs are activated and regulate a variety of physiological responses. It has been widely accepted that GPCRs can self-associate as dimers or higher-order oligomers even though protomeric GPCR is capable of activating heterotrimeric G proteins and recruiting arrestins. Although GPCR complexes have been suggested to possess distinct functional properties such as receptor trafficking, receptor phosphorylation, biased downstream signaling, and allosteric communication, the stability and the structural mechanisms for the dimerization of class A GPCRs have not been extensively studied. The β2 adrenergic receptor (β2AR) is a prototype of class A GPCRs and is probably the most extensively studied among the currently available high resolution crystal structures of GPCRs. However, lack of clear dimer interface and the controversy of the stability of β2AR dimeric complexes brings to the question that whether β2AR self-associate as a stable dimer.