Transcription profiling in human platelets reveals LRRFIP1 as a novel protein regulating platelet function.
ABSTRACT Within the healthy population, there is substantial, heritable, and interindividual variability in the platelet response. We explored whether a proportion of this variability could be accounted for by interindividual variation in gene expression. Through a correlative analysis of genome-wide platelet RNA expression data from 37 subjects representing the normal range of platelet responsiveness within a cohort of 500 subjects, we identified 63 genes in which transcript levels correlated with variation in the platelet response to adenosine diphosphate and/or the collagen-mimetic peptide, cross-linked collagen-related peptide. Many of these encode proteins with no reported function in platelets. An association study of 6 of the 63 genes in 4235 cases and 6379 controls showed a putative association with myocardial infarction for COMMD7 (COMM domain-containing protein 7) and a major deviation from the null hypo thesis for LRRFIP1 [leucine-rich repeat (in FLII) interacting protein 1]. Morpholino-based silencing in Danio rerio identified a modest role for commd7 and a significant effect for lrrfip1 as positive regulators of thrombus formation. Proteomic analysis of human platelet LRRFIP1-interacting proteins indicated that LRRFIP1 functions as a component of the platelet cytoskeleton, where it interacts with the actin-remodeling proteins Flightless-1 and Drebrin. Taken together, these data reveal novel proteins regulating the platelet response.
- Future Cardiology 01/2014; 10(1):9-12.
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ABSTRACT: BAMBI is a transmembrane protein related to the transforming growth factor-β superfamily, and is highly expressed in platelets and endothelial cells. We previously demonstrated its positive role in thrombus formation using a zebrafish thrombosis model. In the present study, we used Bambi-deficient mice and radiation chimeras to evaluate the function of this receptor in the regulation of both hemostasis and thrombosis. We show that Bambi(-/-) and Bambi(+/-) mice exhibit mildly prolonged bleeding times compared to Bambi(+/+) littermates. In addition, using two in vivo thrombosis models in mesenterium or cremaster muscle arterioles, we demonstrate that Bambi-deficient mice form unstable thrombi compared to Bambi(+/+) mice. No defects in thrombin generation in Bambi(-/-) mouse plasma could be detected ex vivo. Moreover, the absence of BAMBI had no effect on platelet counts, platelet activation, aggregation or platelet procoagulant function. Similar to Bambi(-/-) mice, Bambi(-/-) transplanted with Bambi(+/+) bone marrow formed unstable thrombi in the laser-induced thrombosis model that receded more rapidly than thrombi that formed in Bambi(+/+) mice receiving Bambi(-/-) bone marrow transplants. Taken together, these results provide strong evidence for an important role of endothelium, rather than platelet BAMBI as a positive regulator of both thrombus formation and stability.Blood 03/2014; · 9.78 Impact Factor
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ABSTRACT: Lrrfip1 is an up-regulated protein after cerebral ischaemia whose precise role in the brain both in healthy and ischaemic conditions is unclear. Different Lrrfip1 isoforms with distinct roles have been reported in human and mouse species. The present study aimed to analyse the Lrrfip1 transcriptional variants expressed in rat cortex, to characterise their expression patterns and subcellular location after ischaemia, and to define their putative role in the brain. Five transcripts were identified and three of them (Lrrfip1, CRA_g and CRA_a' (Flap-1)) were analysed by qPCR. All the transcripts were up-regulated and showed differential expression patterns after in-vivo and in-vitro ischaemia models. The main isoform, Lrrfip1, was found to be up-regulated from the acute to the late phases of ischaemia in the cytoplasm of neurons and astrocytes of the peri-infarct area. This study demonstrates that Lrrfip1 activates β-catenin, Akt, and mTOR proteins in astrocytes and positively regulates the expression of the glutamate transporter GLT-1. Our findings point to Lrrfip1 as a key brain protein that regulates pro-survival pathways and proteins and encourages further studies to elucidate its role in cerebral ischaemia as a potential target to prevent brain damage and promote functional recovery after stroke.Neuroscience 03/2014; · 3.12 Impact Factor