Identification of a cytoplasmic linker protein as a potential target for neovascularization

A cilium-independent role for intraflagellar transport 88 in regulating angiogenesis

Endothelial cilia are microtubule-based hair-like protrusions in the lumen ofblood vessels that function as fluid mechanosensors to regulate vascular hemodynamics.However, the functions of endothelial cilia in vascular development remain controversial. In this study, depletion of several key proteins responsible for ciliogenesis allows us to identify a cilium-independent role for intraflagellartransport88 (IFT88) in mammalian angiogenesis. Disruption of primary cilia by heat shock does not affect the angiogenic process. However, depletion of IFT88 significantly inhibits angiogenesis both in vitro and in vivo. IFT88 mediates angiogenesis by regulating the migration, polarization, proliferation, and oriented division of vascular endothelial cells. Further mechanistic studies demonstrate that IFT88 interacts with γ-tubulin and microtubule plus-end tracking proteins and promotes microtubule stability. Our findings indicate that IFT88 regulates angiogenesis through its actions in microtubule-based cellular processes, independent of its role in ciliogenesis.

Long noncoding RNA ANRIL regulates endothelial cell activities associated with coronary artery disease by up-regulating CLIP1, EZR, and LYVE1 genes

Coronary artery disease (CAD) is the leading cause of death worldwide. Long noncoding RNAs (lncRNAs) are a class of noncoding transcripts of > 200 nucleotides and are increasingly recognized as playing functional roles in physiology and disease. ANRIL is an lncRNA gene mapped to the chromosome 9p21 genetic locus for CAD identified by the first series of genome-wide association studies (GWAS). However, ANRIL's role in CAD and the underlying molecular mechanism are unknown. Here, we show that the major ANRIL transcript in endothelial cells (ECs) is DQ485454 with a much higher expression level in ECs than in THP-1 monocytes. Of note, DQ485454 expression was down-regulated in CAD coronary arteries compared with non-CAD arteries. DQ485454 overexpression significantly reduced monocyte adhesion to ECs, transendothelial monocyte migration (TEM), and EC migration, which are critical cellular processes involved in CAD initiation, whereas siRNA-mediated ANRIL knockdown (KD) had the opposite effect. Microarray and follow-up quantitative RT-PCR analyses revealed that the ANRIL KD down-regulated expression of AHNAK2, CLIP1, CXCL11, ENC1, EZR, LYVE1, WASL, and TNFSF10 genes and up-regulated TMEM100 and TMEM106B genes. Mechanistic studies disclosed that overexpression of CLIP1, EZR, and LYVE1 reversed the effects of ANRIL KD on monocyte adhesion to ECs, TEM, and EC migration. These findings indicate that ANRIL regulates EC functions directly related to CAD, supporting the hypothesis that ANRIL is involved in CAD pathogenesis at the 9p21 genetic locus and identifying a molecular mechanism underlying lncRNA-mediated regulation of EC function and CAD development.

Effects of FSTL1 on the proliferation and motility of breast cancer cells and vascular endothelial cells

Background

Treatments that prevent the motility of breast cancer cells and inhibit formation of new capillary vessels are urgently needed. FSTL1 is a secreted protein that has been implicated in maintaining the normal physiological function of the cardiovascular system, in addition to a variety of other biological functions. We investigated the role of FSTL1 in the proliferation and migration of breast cancer and vascular endothelial cells.

Methods

Human umbilical vein endothelial cells and human breast cancer BT‐549 cells were used to test the effects of FSTL1 and the N‐terminal domain of FSTL1. Immunofluorescence microscopy and 3‐(4, 5‐dimethylthiazolyl‐2)‐2,5‐diphenyltetrazolium bromide, transwell invasion, and wound healing assays were conducted.

Results

Different doses of the N‐terminal fragment of FSTL1 (FSTL‐N) have variable effects on the migration of these cells. However, FSTL1 does not significantly affect tube formation in vitro from vascular endothelial cells. FSTL1‐FL and FSTL1‐N have modest effects on the invasion of breast cancer and vascular endothelial cells. Interestingly, FSTL1‐FL, but not FSTL‐N, modulates vascular endothelial cell polarization.

Conclusion

FSTL1 modestly affects the proliferation of breast cancer cells and vascular endothelial cells. Our findings improve our understanding of the functions of FSTL1 in breast cancer development and angiogenesis.

STAT3 association with microtubules and its activation are independent of HDAC6 activity

Signal transducer and activator of transcription 3 (STAT3) is an important oncogenic transcription factor residing in the cytoplasm in the resting cells. Upon stimulation, STAT3 is activated and translocated to the nucleus to regulate target genes. Although the canonical transcriptional function of STAT3 has been intensively studied, less is known about its cytoplasmic localization. In this study, by immunoprecipitation, microtubule cosedimentation, and immunofluorescence assays, we present the first evidence that cytoplasmic STAT3 interacts with both tubulin and microtubules. By using small-molecule inhibitor approaches, we further demonstrate that the localization of STAT3 on microtubules and its activation are independent of histone deacetylase 6 (HDAC6) activity. In addition, disruption of microtubule dynamics does not alter the activation and nuclear translocation of STAT3 in response to interleukin-6 treatment. These findings reveal that cytoplasmic STAT3 is physically associated with microtubules, whereas its activation and nuclear translocation are independent of microtubule dynamics, implicating that the association of STAT3 with microtubules might be involved in the regulation of noncanonical functions of STAT3 in the cytoplasm.

Histone deacetylase 6 activity is critical for the metastasis of Burkitt's lymphoma cells

Background

Burkitt’s lymphoma is an aggressive malignancy with high risk of metastasis to extranodal sites, such as bone marrow and central nervous system. The prognosis of metastatic Burkitt’s lymphoma is poor. Here we sought to identify a role of histone deacetylase 6 (HDAC6) in the metastasis of Burkitt’s lymphoma cells.

Methods

Burkitt’s lymphoma cells were pharmacologically treated with niltubacin, tubacin or sodium butyrate (NaB) or transfected with siRNAs to knock down the expression of HDAC6. Cell migration and invasion ability were measured by transwell assay, and cell cycle progression was analyzed by flow cytometry. Cell adhesion and proliferation was determined by CellTiter-Glo luminescent cell viability assay kit. Cell morphological alteration and microtubule stability were analyzed by immunofluorescence staining. Effect of niltubacin, tubacin and NaB on acetylated tubulin and siRNA efficacy were measured by western blotting.

Results

Suppression of histone deacetylase 6 activity significantly compromised the migration and invasion of Burkitt’s lymphoma cells, without affecting cell proliferation and cell cycle progression. Mechanistic study revealed that HDAC6 modulated chemokine induced cell shape elongation and cell adhesion probably through its action on microtubule dynamics.

Conclusions

We identified a critical role of HDAC6 in the metastasis of Burkitt’s lymphoma cells, suggesting that pharmacological inhibition of HDAC6 could be a promising strategy for the management of metastatic Burkitt’s lymphoma.

Identification of a role for the PI3K/AKT/mTOR signaling pathway in innate immune cells

The innate immune system is the first line of host defense against infection and involves several different cell types. Here we investigated the role of the phosphatidylinositol 3 kinase (PI3K) signaling pathway in innate immune cells. By blocking this pathway with pharmacological inhibitors, we found that the production of proinflammatory cytokines was drastically suppressed in monocytes and macrophages. Further study revealed that the suppression was mainly related to the mammalian target of rapamycin (mTOR)/p70^S6K signaling. In addition, we found that the PI3K pathway was involved in macrophage motility and neovascularization. Our data provide a rationale that inhibition of the PI3K signaling pathway could be an attractive approach for the management of inflammatory disorders.