Brothers and Sisters: Molecular Insights Into Arterial-Venous Heterogeneity

The molecular differences between arteries and veins are genetically predetermined and are evident even before the first embryonic heart beat. Although ephrinB2 and EphB4 are expressed in cells that will ultimately differentiate into arteries and veins respectively, many other genes have been shown to play a significant role in cell fate determination. The expression patterns of ephrinB2 and EphB4 are restricted to arterial-venous boundaries, and Eph/ephrin signaling provides repulsive cues at arterial-venous boundaries that are thought to prevent intermixing of arterial- and venous-fated cells. However, the maintenance of arterial-venous fate is susceptible to some degree of plasticity. Thus, in response to signals from the ambient microenvironment and shear stress, there is flow-mediated intercalation of the arteries and veins that ultimately leads to the formation of a functional, closed-loop circulation. In addition, cells in the blood vessels of each organ undergo epigenetic, morphologic and functional adaptive changes that are specific to the proximate function of their cognate organ(s). These adaptive changes result in an inter-organ and intra-organ vessel heterogeneity that manifest clinically in a disparate response of different organs to identical risk factors and injury in the same animal. In this review, we will focus on the molecular and physiologic factors influencing arterial-venous heterogeneity between and within different organ(s). We will explore arterial-venous differences in selected organs as well as their respective endothelial cell architectural organization that results in their inter- and intra-organ heterogeneity

Tear Me Down: Role of Calpain in the Development of Cardiac Ventricular Hypertrophy

Cardiac hypertrophy develops most commonly in response to hypertension and is an independent risk factor for the development of heart failure. The mechanisms by which cardiac hypertrophy may be reversed to reduce this risk have not been fully determined to the point where mechanism-specific therapies have been developed. Recently, proteases in the calpain family have been implicated in regulating the development of cardiac hypertrophy in preclinical animal models. In this review, we summarize the molecular mechanisms by which calpain inhibition has been shown to modulate the development of cardiac (specifically ventricular) hypertrophy. The context within which calpain inhibition might be developed for therapeutic intervention of cardiac hypertrophy is then discussed

Back to your heart: Ubiquitin proteasome system-regulated signal transduction

Awareness of the regulation of cell signaling by post-translational ubiquitination has emerged over the past 2 decades. Like phosphorylation, post-translational modification of proteins with ubiquitin can result in the regulation of numerous cellular functions, for example, the DNA damage response, apoptosis, cell growth, and the innate immune response. In this review, we discuss recently published mechanisms by which the ubiquitin proteasome system regulates key signal transduction pathways in the heart, including MAPK JNK, calcineurin, FOXO, p53, and estrogen receptors α and β. We then explore how ubiquitin proteasome system-specific regulation of these signal transduction pathways plays a role in the pathophysiology of common cardiac diseases, such as cardiac hypertrophy, heart failure, ischemia reperfusion injury, and diabetes

Regulation of ankyrin repeat and suppressor of cytokine signalling box protein 4 expression in the immortalized murine endothelial cell lines MS1 and SVR: a role for tumour necrosis factor alpha and oxygen: REGULATION OF ASB4 EXPRESSION IN ENDOTHELIAL CELL LINES

During vascular development, endothelial cells are exposed to a variety of rapidly changing factors, including fluctuating oxygen levels. We have previously shown that Ankyrin Repeat and SOCS Box Protein 4 (ASB4) is the most highly differentially expressed gene in the vascular lineage during early differentiation and is expressed in the embryonic vasculature at a time when oxygen tension is rising due to the onset of placental blood flow. In order to further our understanding of the regulation of ASB4 expression in endothelial cells, we tested the effect of various stressors for their ability to alter ASB4 expression in the immortalized murine endothelial cell lines MS1 and SVR. ASB4 expression is decreased during hypoxic insult and shear stress whereas it is increased in response to TNF-α. Further investigation indicated that Nuclear Factor kappa B (NF-κB) is the responsible transcription factor involved in the TNF-α-induced upregulation of ASB4, placing ASB4 downstream of NF-κB in the TNF-α signaling cascade and identifying it as a potential regulator for TNF-α’s numerous functions associated with inflammation, angiogenesis and apoptosis

LRP1-Dependent Endocytic Mechanism Governs the Signaling Output of the Bmp System in Endothelial Cells and in Angiogenesis

Among the extracellular modulators of Bmp (bone morphogenetic protein) signaling, Bmper (Bmp endothelial cell precursor-derived regulator) both enhances and inhibits Bmp signaling. Recently we found that Bmper modulates Bmp4 activity via a concentration-dependent, endocytic trap-and-sink mechanism

Ataxia and hypogonadism caused by the loss of ubiquitin ligase activity of the U box protein CHIP

Gordon Holmes syndrome (GHS) is a rare Mendelian neurodegenerative disorder characterized by ataxia and hypogonadism. Recently, it was suggested that disordered ubiquitination underlies GHS though the discovery of exome mutations in the E3 ligase RNF216 and deubiquitinase OTUD4. We performed exome sequencing in a family with two of three siblings afflicted with ataxia and hypogonadism and identified a homozygous mutation in STUB1 ({"type":"entrez-nucleotide","attrs":{"text":"NM_005861","term_id":"645912988","term_text":"NM_005861"}}NM_005861) c.737C→T, p.Thr246Met, a gene that encodes the protein CHIP (C-terminus of HSC70-interacting protein). CHIP plays a central role in regulating protein quality control, in part through its ability to function as an E3 ligase. Loss of CHIP function has long been associated with protein misfolding and aggregation in several genetic mouse models of neurodegenerative disorders; however, a role for CHIP in human neurological disease has yet to be identified. Introduction of the Thr246Met mutation into CHIP results in a loss of ubiquitin ligase activity measured directly using recombinant proteins as well as in cell culture models. Loss of CHIP function in mice resulted in behavioral and reproductive impairments that mimic human ataxia and hypogonadism. We conclude that GHS can be caused by a loss-of-function mutation in CHIP. Our findings further highlight the role of disordered ubiquitination and protein quality control in the pathogenesis of neurodegenerative disease and demonstrate the utility of combining whole-exome sequencing with molecular analyses and animal models to define causal disease polymorphisms

Tobacco use induces anti-apoptotic, proliferative patterns of gene expression in circulating leukocytes of Caucasian males

Abstract Background Strong epidemiologic evidence correlates tobacco use with a variety of serious adverse health effects, but the biological mechanisms that produce these effects remain elusive. Results We analyzed gene transcription data to identify expression spectra related to tobacco use in circulating leukocytes of 67 Caucasian male subjects. Levels of cotinine, a nicotine metabolite, were used as a surrogate marker for tobacco exposure. Significance Analysis of Microarray and Gene Set Analysis identified 109 genes in 16 gene sets whose transcription levels were differentially regulated by nicotine exposure. We subsequently analyzed this gene set by hyperclustering, a technique that allows the data to be clustered by both expression ratio and gene annotation (e.g. Gene Ontologies). Conclusion Our results demonstrate that tobacco use affects transcription of groups of genes that are involved in proliferation and apoptosis in circulating leukocytes. These transcriptional effects include a repertoire of transcriptional changes likely to increase the incidence of neoplasia through an altered expression of genes associated with transcription and signaling, interferon responses and repression of apoptotic pathways

CHIP Deficiency Decreases Longevity, with Accelerated Aging Phenotypes Accompanied by Altered Protein Quality Control▿

During the course of biological aging, there is a gradual accumulation of damaged proteins and a concomitant functional decline in the protein degradation system. Protein quality control is normally ensured by the coordinated actions of molecular chaperones and the protein degradation system that collectively help to maintain protein homeostasis. The carboxyl terminus of Hsp70-interacting protein (CHIP), a ubiquitin ligase/cochaperone, participates in protein quality control by targeting a broad range of chaperone substrates for proteasome degradation via the ubiquitin-proteasome system, demonstrating a broad involvement of CHIP in maintaining cytoplasmic protein quality control. In the present study, we have investigated the influence that protein quality control exerts on the aging process by using CHIP−/− mice. CHIP deficiency in mice leads to a markedly reduced life span, along with accelerated age-related pathophysiological phenotypes. These features were accompanied by indications of accelerated cellular senescence and increased indices of oxidative stress. In addition, CHIP−/− mice exhibit a deregulation of protein quality control, as indicated by elevated levels of toxic oligomer proteins and a decline in proteasome activity. Taken together, these data reveal that impaired protein quality control contributes to cellular senescence and implicates CHIP-dependent quality control mechanisms in the regulation of mammalian longevity in vivo

LRP1-Dependent Endocytic Mechanism Governs the Signaling Output of the Bmp System in Endothelial Cells and in Angiogenesis

RATIONALE: Among the extracellular modulators of Bmp (bone morphogenetic protein) signaling, Bmper (Bmp endothelial cell precursor-derived regulator) both enhances and inhibits Bmp signaling. Recently we found that Bmper modulates Bmp4 activity via a concentration-dependent, endocytic trap-and-sink mechanism. OBJECTIVE: To investigate the molecular mechanisms required for endocytosis of the Bmper/Bmp4 and signaling complex and determine the mechanism of Bmper’s differential effects on Bmp4 signaling. METHODS AND RESULTS: Using an array of biochemical and cell biology techniques, we report that LRP1 (Low density lipoprotein receptor-related protein 1), a member of the LDL receptor family, acts as an endocytic receptor for Bmper and a co-receptor of Bmp4 to mediate the endocytosis of the Bmper/Bmp4 signaling complex. Furthermore, we demonstrate that LRP1-dependent Bmper/Bmp4 endocytosis is essential for Bmp4 signaling, as evidenced by the phenotype of lrp1-deficient zebrafish, which have abnormal cardiovascular development and decreased Smad1/5/8 activity in key vasculogenic structures. CONCLUSIONS: Together, these data reveal a novel role for LRP1 in the regulation of Bmp4 signaling by regulating receptor complex endocytosis. In addition, these data introduce LRP1 as a critical regulator of vascular development. These observations demonstrate Bmper’s ability to fine-tune Bmp4 signaling at the single-cell level, unlike the spatial regulatory mechanisms applied by other Bmp modulators