In this task, you are given an abstract of article. Your task is to generate title for this article. Preferred titles are under thirty words.

Q: The bacterial type VI secretion system (T6SS) is a large multicomponent, dynamic macromolecular machine that has an important role in the ecology of many Gram-negative bacteria. T6SS is responsible for translocation of a wide range of toxic effector molecules, allowing predatory cells to kill both prokaryotic as well as eukaryotic prey cells. The T6SS organelle is functionally analogous to contractile tails of bacteriophages and is thought to attack cells by initially penetrating them with a trimeric protein complex called the VgrG spike. Neither the exact protein composition of the T6SS organelle nor the mechanisms of effector selection and delivery are known. Here we report that proteins from the PAAR (proline-alanine-alanine-arginine) repeat superfamily form a sharp conical extension on the VgrG spike, which is further involved in attaching effector domains to the spike. The crystal structures of two PAAR-repeat proteins bound to VgrG-like partners show that these proteins sharpen the tip of the T6SS spike complex. We demonstrate that PAAR proteins are essential for T6SS-mediated secretion and target cell killing by Vibrio cholerae and Acinetobacter baylyi. Our results indicate a new model of the T6SS organelle in which the VgrG-PAAR spike complex is decorated with multiple effectors that are delivered simultaneously into target cells in a single contraction-driven translocation event.

A: PAAR-repeat proteins sharpen and diversify the Type VI secretion system spike
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Q: Recent research has shown that adipose tissues contain abundant MSCs (mesenchymal stem cells). The origin and location of the adipose stem cells, however, remain unknown, presenting an obstacle to the further purification and study of these cells. In the present study, we aimed at investigating the origins of adipose stem cells. -SMA (-smooth muscle actin) is one of the markers of pericytes. We harvested ASCs (adipose stromal cells) from -SMA-GFP (green fluorescent protein) transgenic mice and sorted them into GFP-positive and GFP-negative cells by FACS. Multilineage differentiation tests were applied to examine the pluripotent ability of the -SMA-GFP-positive and -negative cells. Immunofluorescent staining for -SMA and PDGF-R (platelet-derived growth factor receptor ) were applied to identify the -SMA-GFP-positive cells. Then -SMA-GFP-positive cells were loaded on a collagen-fibronectin gel with endothelial cells to test their vascularization ability both in vitro and in vivo. Results show that, in adipose tissue, all of the -SMA-GFP-positive cells congregate around the blood vessels. Only the -SMA-GFP-positive cells have multilineage differentiation ability, while the -SMA-GFP-negative cells can only differentiate in an adipogenic direction. The -SMA-GFP-positive cells maintained expression of -SMA during multilineage differentiation. The -SMA-GFP-positive cells can promote the vascularization of endothelial cells in three-dimensional culture both in vitro and in vivo. We conclude that the adipose stem cells originate from perivascular cells and congregate around blood vessels.

A: Adipose stem cells originate from perivascular cells.
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Q: Angiogenesis is a necessary step in tumor growth and metastasis. It is well established that the metabolites of omega-6 and omega-3 fatty acids, which must be obtained through the diet and cannot be synthesized de novo in mammals, have differential effects on cellular processes. Omega-6 fatty acid (n6 FA)-derived metabolites promote angiogenesis by increasing growth factor expression whereas omega-3 fatty acids (n3 FA) have anti-angiogenic and antitumor properties. However, most studies thus far have failed to account for the role of the n6 FA/n3 FA ratio in angiogenesis and instead examined the absolute levels of n6 and n3 FA. This review highlights the biochemical interactions between n6 and n3 FA and focuses on how the n6/n3 FA ratio in tissues modulates tumor angiogenesis. We suggest that future work should consider the n6/n3 FA ratio to be a key element in experimental design and analysis. Furthermore, we recommend that clinical interventions should aim to both reduce n6 metabolites and simultaneously increase n3 FA intake.

A:
The role of the tissue omega-6/omega-3 fatty acid ratio in regulating tumor angiogenesis
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