scholarly journals An alternate covalent form of platelet αIIbβ3 integrin that resides in focal adhesions and has altered function

Blood ◽  
2021 ◽  
Author(s):  
Aster Pijning ◽  
Mitchell Blyth ◽  
Michelle Coote ◽  
Freda H. Passam ◽  
Joyce Chiu ◽  
...  
Keyword(s):  
Disulfide Bond ◽  
Cultured Cells ◽  
Focal Adhesions ◽  
Adaptor Protein ◽  
Integrin Receptor ◽  
Surface Distribution ◽  
Platelet Surface ◽  
Form And Function ◽  
And Function ◽  
Αiibβ3 Integrin

The αIIbβ3 integrin receptor coordinates platelet adhesion, activation and mechanosensing in thrombosis and haemostasis. Using differential cysteine alkylation and mass spectrometry, we have identified a disulfide bond in the αIIb subunit linking cysteines 490 and 545 that is missing in about one in three integrin molecules on the resting and activated human platelet surface. This alternate covalent form of αIIbβ3 is pre-determined as it is also produced by human megakaryoblasts and baby hamster kidney fibroblasts (BHK) transfected with recombinant integrin. From co-immunoprecipitation experiments, the alternate form selectively partitions into focal adhesions on the activated platelet surface. Its function was evaluated in BHK cells expressing a mutant integrin with an ablated C490-C545 disulfide bond. The disulfide mutant integrin has functional outside-in signalling but extended residency time in focal adhesions due to reduced rate of clathrin-mediated integrin internalisation and recycling, which is associated with enhanced affinity of the αIIb subunit for clathrin adaptor protein-2. Molecular dynamics simulations indicate that the alternate covalent form of αIIb requires higher forces to transition from bent to open conformational states that is in accordance with reduced affinity for fibrinogen and activation by manganese ions. These findings indicate that the αIIbβ3 integrin receptor is produced in different covalent forms that have different cell surface distribution and function. The C490, C545 cysteine pair is conserved across all 18 integrin α subunits and the disulfide bond in the αV and α2 subunits in cultured cells is similarly missing, suggesting that this alternate integrin form and function is also conserved.

scholarly journals Phosphoproteomic quantitation and causal analysis reveal pathways in GPVI/ITAM-mediated platelet activation programs

Blood ◽  
2020 ◽  
Vol 136 (20) ◽  
pp. 2346-2358 ◽  
Author(s):  
Özgün Babur ◽  
Alexander R. Melrose ◽  
Jennifer M. Cunliffe ◽  
John Klimek ◽  
Jiaqing Pang ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Intracellular Signaling ◽  
Vascular Inflammation ◽  
Functional Screening ◽  
Tandem Mass ◽  
Rab Gtpases ◽  
Platelet Surface ◽  
Form And Function ◽  
Signaling Mechanisms ◽  
And Function

Abstract Platelets engage cues of pending vascular injury through coordinated adhesion, secretion, and aggregation responses. These rapid, progressive changes in platelet form and function are orchestrated downstream of specific receptors on the platelet surface and through intracellular signaling mechanisms that remain systematically undefined. This study brings together cell physiological and phosphoproteomics methods to profile signaling mechanisms downstream of the immunotyrosine activation motif (ITAM) platelet collagen receptor GPVI. Peptide tandem mass tag (TMT) labeling, sample multiplexing, synchronous precursor selection (SPS), and triple stage tandem mass spectrometry (MS3) detected >3000 significant (false discovery rate < 0.05) phosphorylation events on >1300 proteins over conditions initiating and progressing GPVI-mediated platelet activation. With literature-guided causal inference tools, >300 site-specific signaling relations were mapped from phosphoproteomics data among key and emerging GPVI effectors (ie, FcRγ, Syk, PLCγ2, PKCδ, DAPP1). Through signaling validation studies and functional screening, other less-characterized targets were also considered within the context of GPVI/ITAM pathways, including Ras/MAPK axis proteins (ie, KSR1, SOS1, STAT1, Hsp27). Highly regulated GPVI/ITAM targets out of context of curated knowledge were also illuminated, including a system of >40 Rab GTPases and associated regulatory proteins, where GPVI-mediated Rab7 S72 phosphorylation and endolysosomal maturation were blocked by TAK1 inhibition. In addition to serving as a model for generating and testing hypotheses from omics datasets, this study puts forth a means to identify hemostatic effectors, biomarkers, and therapeutic targets relevant to thrombosis, vascular inflammation, and other platelet-associated disease states.

Scanning tunneling microscopy (STM) of DNA and RNA

1989 ◽  
Vol 47 ◽  
pp. 34-35
Author(s):  
Patricia G. Arscott ◽  
Gil Lee ◽  
Victor A. Bloomfield ◽  
D. Fennell Evans
Keyword(s):  
Molecular Structures ◽  
Inorganic Materials ◽  
Resolving Power ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Form And Function ◽  
Dna And Rna ◽  
Calf Thymus ◽  
And Function ◽  
The Relationship

STM is one of the most promising techniques available for visualizing the fine details of biomolecular structure. It has been used to map the surface topography of inorganic materials in atomic dimensions, and thus has the resolving power not only to determine the conformation of small molecules but to distinguish site-specific features within a molecule. That level of detail is of critical importance in understanding the relationship between form and function in biological systems. The size, shape, and accessibility of molecular structures can be determined much more accurately by STM than by electron microscopy since no staining, shadowing or labeling with heavy metals is required, and there is no exposure to damaging radiation by electrons. Crystallography and most other physical techniques do not give information about individual molecules.We have obtained striking images of DNA and RNA, using calf thymus DNA and two synthetic polynucleotides, poly(dG-me5dC)·poly(dG-me5dC) and poly(rA)·poly(rU).

Re-examining the form and function of superstition

2011 ◽  
Author(s):  
Scott Fluke ◽  
Russell J. Webster ◽  
Donald A. Saucier
Keyword(s):  
Form And Function ◽  
And Function

A New Form and Function for Personality

2013 ◽  
Author(s):  
Joshua Wilt ◽  
William Revelle
Keyword(s):  
Form And Function ◽  
New Form ◽  
And Function

Role of the 807 C/T Polymorphism of the α2 Gene in Platelet GP Ia Collagen Receptor Expression and Function

1999 ◽  
Vol 81 (06) ◽  
pp. 951-956 ◽  
Author(s):  
J. Corral ◽  
R. González-Conejero ◽  
J. Rivera ◽  
F. Ortuño ◽  
P. Aparicio ◽  
...  
Keyword(s):  
Venous Thrombosis ◽  
Cell Types ◽  
Receptor Expression ◽  
Case Control Studies ◽  
Platelet Surface ◽  
Vitro Analysis ◽  
And Function ◽  
In Vitro Analysis

SummaryThe variability of the platelet GP Ia/IIa density has been associated with the 807 C/T polymorphism (Phe 224) of the GP Ia gene in American Caucasian population. We have investigated the genotype and allelic frequencies of this polymorphism in Spanish Caucasians. The T allele was found in 35% of the 284 blood donors analyzed. We confirmed in 159 healthy subjects a significant association between the 807 C/T polymorphism and the platelet GP Ia density. The T allele correlated with high number of GP Ia molecules on platelet surface. In addition, we observed a similar association of this polymorphism with the expression of this protein in other blood cell types. The platelet responsiveness to collagen was determined by “in vitro” analysis of the platelet activation and aggregation response. We found no significant differences in these functional platelet parameters according to the 807 C/T genotype. Finally, results from 3 case/control studies involving 302 consecutive patients (101 with coronary heart disease, 104 with cerebrovascular disease and 97 with deep venous thrombosis) determined that the 807 C/T polymorphism of the GP Ia gene does not represent a risk factor for arterial or venous thrombosis.

Ausnahmesegment

2018 ◽  
Vol 48 (191) ◽  
Author(s):  
Barbara Schönig
Keyword(s):  
Welfare State ◽  
Social Housing ◽  
Integrated Approach ◽  
New Paradigm ◽  
Development Models ◽  
Form And Function ◽  
Institutional Organization ◽  
National Welfare ◽  
And Function ◽  
The Welfare State

Going along with the end of the “golden age” of the welfare state, the fordist paradigm of social housing has been considerably transformed. From the 1980s onwards, a new paradigm of social housing has been shaped in Germany in terms of provision, institutional organization and design. This transformation can be interpreted as a result of the interplay between the transformation of national welfare state and housing policies, the implementation of entrepreneurial urban policies and a shift in architectural and urban development models. Using an integrated approach to understand form and function of social housing, the paper characterizes the new paradigm established and nevertheless interprets it within the continuity of the specific German welfare resp. housing regime, the “German social housing market economy”.

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