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Our results suggest that MAGL may contribute to the pathophysiology of focal cerebral ischemia and is thus a promising therapeutic target for the treatment of ischemic stroke.

P-element vectors are commonly used to make transgenic Drosophila and generally insert in the genome in a nonselective manner. However, when specific fragments of regulatory DNA from a few Drosophila genes are incorporated into P-transposons, they cause the vectors to be inserted near the gene from which the DNA fragment was derived. This is called P-element homing. We mapped the minimal DNA fragment that could mediate homing to the engrailed/invected region of the genome. A 1.6 kb fragment of engrailed regulatory DNA that contains two Polycomb-group response elements (PREs) was sufficient for homing. We made flies that contain a 1.5kb deletion of engrailed DNA (enΔ1.5) in situ, including the PREs and the majority of the fragment that mediates homing. Remarkably, homing still occurs onto the enΔ1. 5 chromosome. In addition to homing to en, P[en] inserts near Polycomb group target genes at an increased frequency compared to P[EPgy2], a vector used to generate 18,214 insertions for the Drosophila gene disruption project. We suggest that homing is mediated by interactions between multiple proteins bound to the homing fragment and proteins bound to multiple areas of the engrailed/invected chromatin domain. Chromatin structure may also play a role in homing.

Thoracic aortic aneurysm and dissection (TAAD) is a deadly disease characterized by intimal disruption induced by hemodynamic forces of the circulation. The effect of exercise in patients with TAAD is largely unknown. β-aminopropionitrile (BAPN) is an irreversible inhibitor of lysyl oxidase that induces TAAD in mice. The objective of this study was to investigate the effect of aerobic exercise on BAPN-induced TAAD. Upon weaning, mice were given either BAPN-containing water or standard drinking water and subjected to either conventional cage activity (BAPN-CONV) or forced treadmill exercise (BAPN-EX) for up to 26 weeks. Mortality was 23.5% (20/85) for BAPN-CONV mice versus 0% (0/22) for BAPN-EX mice (Hazard Ratio 3.8; p=0.01). BAPN induced significant elastic lamina fragmentation and intimal-medial thickening compared with BAPN-untreated controls, and aneurysms were identified in 50% (5/10) of mice that underwent contrast-enhanced CT scanning. Exercise significantly decreased BAPN-induced wall thickening, calculated circumferential wall tension, and lumen diameter, with 0% (0/5) of BAPN-EX demonstrating chronic aortic aneurysm formation on CT scan. Expression of selected genes relevant to vascular diseases were analyzed by qRT-PCR. Notably, exercise normalized BAPN-induced increases in TGFβ pathway related genes Cd109, Smad4, and Tgfβr1, inflammation related genes Vcam1, Bcl2a1, Ccr2, Pparg, Il1r1, Il1r1, Itgb2, and Itgax, as well as vascular injury and response related genes Mmp3, Fn1, and Vwf. Additionally, exercise significantly increased elastin expression in BAPN-treated animals compared with controls. This study suggests that moderate aerobic exercise may be safe and effective in preventing the most devastating outcomes in TAAD.

Matrix metalloprotease (MMP) activation contributes to the degradation of the extracellular matrix (ECM), resulting in a multitude of pathologies. Low-density lipoprotein receptor-related protein 1 (LRP1) is a multifaceted endocytic and signaling receptor that is responsible for internalization and lysosomal degradation of diverse proteases, protease inhibitors, and lipoproteins along with numerous other proteins. In this study, we identified MMP-1 as a novel LRP1 ligand. Binding studies employing surface plasmon resonance revealed that both proMMP-1 and active MMP-1 bind to purified LRP1 with equilibrium dissociation constants (K D) of 19 and 25 nM, respectively. We observed that human aortic smooth muscle cells readily internalize and degrade 125I-labeled proMMP-1 in an LRP1-mediated process. Our binding data also revealed that all tissue inhibitors of metalloproteases (TIMPs) bind to LRP1 with K D values ranging from 23 to 33 nM. Interestingly, the MMP-1/TIMP-1 complex bound to LRP1 with an affinity (K D = 0.6 nM) that was 30-fold higher than that of either component alone, revealing that LRP1 prefers the protease:inhibitor complex as a ligand. Of note, modification of lysine residues on either proMMP-1 or TIMP-1 ablated the ability of the MMP-1/TIMP-1 complex to bind to LRP1. LRP1’s preferential binding to enzyme:inhibitor complexes was further supported by the higher binding affinity for proMMP-9/TIMP-1 complexes than for either of these two components alone. LRP1 has four clusters of ligand-binding repeats, and MMP-1, TIMP-1, and MMP-1/TIMP-1 complexes bound to cluster III most avidly. Our results reveal an important role for LRP1 in controlling ECM homeostasis by regulating MMP-1 and MMP-9 levels.

Aortic aneurysms represent a significant clinical problem as they largely go undetected until a rupture occurs. Currently, an understanding of mechanisms leading to aneurysm formation is limited. Numerous studies clearly indicate that vascular smooth muscle cells play a major role in the development and response of the vasculature to hemodynamic changes and defects in these responses can lead to aneurysm formation. The LDL receptor-related protein 1 (LRP1) is major smooth muscle cell receptor that has the capacity to mediate the endocytosis of numerous ligands and to initiate and regulate signaling pathways. Genetic evidence in humans and mouse models reveal a critical role for LRP1 in maintaining the integrity of the vasculature. Understanding the mechanisms by which this is accomplished represents an important area of research, and likely involves LRP1's ability to regulate levels of proteases known to degrade the extracellular matrix as well as its ability to modulate signaling events.

Background Cognitive decline in Alzheimer’s disease correlates with the spreading of neurofibrillary tangles consisting of aggregated forms of tau from the entorhinal cortex to synaptically connected brain regions. It is unclear how tau aggregation propagates across the brain but may involve trans‐synaptic transfer of tau between neurons or uptake of extracellular tau that is constitutively secreted from neurons. Specific receptors involved in these processes have remained elusive, and here we investigate the hypothesis that the LDL receptor‐related protein 1 (LRP1) functions as an endocytic receptor for tau. Method We employed 125I‐labeled tau to quantify its cellular uptake, confocal microscopy to examine its colocalization with LRP1, and surface plasmon resonance to assess direct binding of tau and phosphorylated forms of tau to LRP1. Result Our results reveal that monomeric tau binds LRP1 with high affinity, while curiously, phosphorylated forms of tau bind LRP1 with much lower affinity. The studies confirm that LRP1 internalization is attenuated the LRP1 antagonist RAP and is reduced by 70% in LRP1‐deficient cells. Confocal microscopy reveals that internalized tau colocalizes with LRP1 in endocytic vesicles. Most of the LRP1‐mediated uptake of tau leads to its lysosomal degradation. We also demonstrate that apolipoprotein E (ApoE) inhibits LRP1‐mediated tau internalization, with the ApoE4 isoform being a more potent inhibitor than other ApoE isoforms. Our studies in LRP1‐deficient cell lines confirm that a RAP‐insensitive second internalization mechanism occurs for tau, suggesting the existence of an LRP1‐independent receptor‐mediated process for tau uptake. Conclusion LRP1 functions as an endocytic receptor for tau, mediating the uptake of monomeric forms of tau resulting in its degradation. The ability of ApoE4 to modulate LRP1‐mediated uptake of tau may disrupt the normal physiological process of tau catabolism, leading to tau uptake by other mechanisms causing the spreading of neurofibrillary tangles and exacerbating the progression of tau‐mediated cognitive loss.

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