The publication data currently available has been vetted by Vanderbilt faculty, staff, administrators and trainees. The data itself is retrieved directly from NCBI's PubMed and is automatically updated on a weekly basis to ensure accuracy and completeness.
If you have any questions or comments, please contact us.
Synaptogenesis requires orchestrated intercellular communication between synaptic partners, with trans-synaptic signals necessarily traversing the extracellular synaptomatrix separating presynaptic and postsynaptic cells. Extracellular matrix metalloproteinases (Mmps) regulated by secreted tissue inhibitors of metalloproteinases (Timps), cleave secreted and membrane-associated targets to sculpt the extracellular environment and modulate intercellular signaling. Here, we test the roles of Mmp at the neuromuscular junction (NMJ) model synapse in the reductionist Drosophila system, which contains just two Mmps (secreted Mmp1 and GPI-anchored Mmp2) and one secreted Timp. We found that all three matrix metalloproteome components co-dependently localize in the synaptomatrix and show that both Mmp1 and Mmp2 independently restrict synapse morphogenesis and functional differentiation. Surprisingly, either dual knockdown or simultaneous inhibition of the two Mmp classes together restores normal synapse development, identifying a reciprocal suppression mechanism. The two Mmp classes co-regulate a Wnt trans-synaptic signaling pathway modulating structural and functional synaptogenesis, including the GPI-anchored heparan sulfate proteoglycan (HSPG) Wnt co-receptor Dally-like protein (Dlp), cognate receptor Frizzled-2 (Frz2) and Wingless (Wg) ligand. Loss of either Mmp1 or Mmp2 reciprocally misregulates Dlp at the synapse, with normal signaling restored by co-removal of both Mmp classes. Correcting Wnt co-receptor Dlp levels in both Mmp mutants prevents structural and functional synaptogenic defects. Taken together, these results identify an Mmp mechanism that fine-tunes HSPG co-receptor function to modulate Wnt signaling to coordinate synapse structural and functional development.
© 2016. Published by The Company of Biologists Ltd.
BACKGROUND - Transient changes in the composition of the myocardial extracellular matrix may contribute to the ventricular systolic dysfunction in stress-induced cardiomyopathy (SIC). We examined the changes in plasma matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) that occur early after the clinical presentation of SIC.
METHODS AND RESULTS - Ten patients with SIC were enrolled. Plasma concentrations of the 6 major MMPs (1, 2, 3, 7, 8, and 9) and all 4 TIMPs (1, 2, 3, and 4) were analyzed and compared with data from 15 control subjects. Within 24 hours of the clinical presentation, SIC patients had lower MMP-1 levels (0.41 ± 0.13 vs 0.70 ± 0.13 pg/mL; P = .048) and MMP-8 levels (1.61 ± 0.34 vs 4.84 ± 1.38 pg/mL; P = .001) and higher TIMP-4 levels (3.06 ± 0.40 vs 2.16 ± 0.18 pg/mL; P = .05) compared with control. Seven of 9 SIC patients had elevated LV end-diastolic pressures, and all had normal LV end-diastolic dimensions and volumes.
CONCLUSIONS - Patients afflicted with SIC had MMP and TIMP profiles similar to those described in hypertensive heart disease and diastolic heart failure and different from the profiles following myocardial infarction. Our findings uncovered a unique biomolecular profile in SIC during the first 24 hours of presentation.
Copyright © 2012 Elsevier Inc. All rights reserved.
Fragile X syndrome (FXS), caused by loss of the fragile X mental retardation 1 (FMR1) product (FMRP), is the most common cause of inherited intellectual disability and autism spectrum disorders. FXS patients suffer multiple behavioral symptoms, including hyperactivity, disrupted circadian cycles, and learning and memory deficits. Recently, a study in the mouse FXS model showed that the tetracycline derivative minocycline effectively remediates the disease state via a proposed matrix metalloproteinase (MMP) inhibition mechanism. Here, we use the well-characterized Drosophila FXS model to assess the effects of minocycline treatment on multiple neural circuit morphological defects and to investigate the MMP hypothesis. We first treat Drosophila Fmr1 (dfmr1) null animals with minocycline to assay the effects on mutant synaptic architecture in three disparate locations: the neuromuscular junction (NMJ), clock neurons in the circadian activity circuit and Kenyon cells in the mushroom body learning and memory center. We find that minocycline effectively restores normal synaptic structure in all three circuits, promising therapeutic potential for FXS treatment. We next tested the MMP hypothesis by assaying the effects of overexpressing the sole Drosophila tissue inhibitor of MMP (TIMP) in dfmr1 null mutants. We find that TIMP overexpression effectively prevents defects in the NMJ synaptic architecture in dfmr1 mutants. Moreover, co-removal of dfmr1 similarly rescues TIMP overexpression phenotypes, including cellular tracheal defects and lethality. To further test the MMP hypothesis, we generated dfmr1;mmp1 double null mutants. Null mmp1 mutants are 100% lethal and display cellular tracheal defects, but co-removal of dfmr1 allows adult viability and prevents tracheal defects. Conversely, co-removal of mmp1 ameliorates the NMJ synaptic architecture defects in dfmr1 null mutants, despite the lack of detectable difference in MMP1 expression or gelatinase activity between the single dfmr1 mutants and controls. These results support minocycline as a promising potential FXS treatment and suggest that it might act via MMP inhibition. We conclude that FMRP and TIMP pathways interact in a reciprocal, bidirectional manner.
BACKGROUND - Cardiac amyloidosis is characterized by amyloid infiltration resulting in extracellular matrix disruption. Amyloid cardiomyopathy due to immunoglobulin light chain protein (AL-CMP) deposition has an accelerated clinical course and a worse prognosis compared with non-light chain cardiac amyloidoses (ie, forms associated with wild-type or mutated transthyretin [TTR]). We therefore tested the hypothesis that determinants of proteolytic activity of the extracellular matrix, the matrix metalloproteinases (MMPs), and their tissue inhibitors (TIMPs) would have distinct patterns and contribute to the pathogenesis of AL-CMP versus TTR-related amyloidosis.
METHODS AND RESULTS - We studied 40 patients with systemic amyloidosis: 10 AL-CMP patients, 20 patients with TTR-associated forms of cardiac amyloidosis, ie, senile systemic amyloidosis (involving wild-type TTR) or mutant TTR, and 10 patients with AL amyloidosis without cardiac involvement. Serum MMP-2 and -9, TIMP-1, -2, and -4, brain natriuretic peptide values, and echocardiography were determined. AL-CMP and TTR-related amyloidosis groups had similar degrees of increased left ventricular wall thickness. However, brain natriuretic peptide, MMP-9, and TIMP-1 levels were distinctly elevated accompanied by marked diastolic dysfunction in the AL-CMP group versus no or minimal increases in the TTR-related amyloidosis group. Brain natriuretic peptide, MMPs, and TIMPs were not correlated with the degree of left ventricular wall thickness but were correlated to each other and to measures of diastolic dysfunction. Immunostaining of human endomyocardial biopsies showed diffuse expression of MMP-9 and TIMP-1 in AL-CMP and limited expression in TTR-related amyloidosis hearts.
CONCLUSIONS - Despite comparable left ventricular wall thickness with TTR-related cardiac amyloidosis, AL-CMP patients have higher brain natriuretic peptide, MMPs, and TIMPs, which correlated with diastolic dysfunction. These findings suggest a relationship between light chains and extracellular matrix proteolytic activation that may play an important role in the functional and clinical manifestations of AL-CMP, distinct from the other non-light chain cardiac amyloidoses.
Previous work has shown that integrin alpha1-null Alport mice exhibit attenuated glomerular disease with decreased matrix accumulation and live much longer than strain-matched Alport mice. However, the mechanism underlying this observation is unknown. Here we show that glomerular gelatinase expression, specifically matrix metalloproteinase-2 (MMP-2), MMP-9, and MMP-14, was significantly elevated in both integrin alpha1-null mice and integrin alpha1-null Alport mice relative to wild-type mice; however, only MMP-9 was elevated in glomeruli of Alport mice that express integrin alpha1. Similarly, cultured mesangial cells from alpha1-null mice showed elevated expression levels of all three MMPs, whereas mesangial cells from Alport mice show elevated expression levels of only MMP-9. In both glomeruli and cultured mesangial cells isolated from integrin alpha1-null mice, activation of the p38 and ERK branches of the mitogen-activated protein kinase pathway was also observed. The use of small molecule inhibitors demonstrated that the activation of the p38, but not ERK, pathway was linked to elevated MMP-2, -9, and -14 expression levels in mesangial cells from integrin alpha1-null mice. In contrast, elevated MMP-9 levels in mesangial cells from Alport mice were linked to ERK pathway activation. Blockade of gelatinase activity using a small molecule inhibitor (BAY-12-9566) ameliorated progression of proteinuria and restored the architecture of the glomerular basement membrane in alpha1 integrin-null Alport mice, suggesting that elevated gelatinase activity exacerbates glomerular disease progression in these mice.
Matrix metalloproteinases (MMPs) are a large conserved family of extracellular proteases, a number of which are expressed during neuronal development and upregulated in nervous system diseases. Primarily on the basis of studies using pharmaceutical inhibitors, MMPs have been proposed to degrade the extracellular matrix to allow growth cone advance during development and hence play largely permissive roles in axon extension. Here we show that MMPs are not required for axon extension in the Drosophila embryo, but rather are specifically required for the execution of several stereotyped motor axon pathfinding decisions. The Drosophila genome contains only two MMP homologs, Mmp1 and Mmp2. We isolated Mmp1 in a misexpression screen to identify molecules required for motoneuron development. Misexpression of either MMP inhibits the regulated separation/defasciculation of motor axons at defined choice points. Conversely, motor nerves in Mmp1 and Mmp2 single mutants and Mmp1 Mmp2 double mutant embryos are loosely bundled/fasciculated, with ectopic axonal projections. Quantification of these phenotypes reveals that the genetic requirement for Mmp1 and Mmp2 is distinct in different nerve branches, although generally Mmp2 plays the predominant role in pathfinding. Using both an endogenous MMP inhibitor and MMP dominant-negative constructs, we demonstrate that MMP catalytic activity is required for motor axon fasciculation. In support of the model that MMPs promote fasciculation, we find that the defasciculation observed when MMP activity is compromised is suppressed by otherwise elevating interaxonal adhesion -- either by overexpressing Fas2 or by reducing Sema-1a dosage. These data demonstrate that MMP activity is essential for embryonic motor axon fasciculation.
The matrix metalloproteinase (MMP) family of extracellular proteases is conserved throughout the animal kingdom. Studies of invertebrate MMPs have demonstrated they are involved in tissue remodeling. In Drosophila, MMPs are required for histolysis, tracheal growth, tissue invasion, axon guidance, and dendritic remodeling. Recent work demonstrates that MMPs also participate in Drosophila tumor invasion. In Caenorhabditis elegans an MMP is involved in anchor cell invasion; a Hydra MMP is important for regeneration and maintaining cell identity; and a sea urchin MMP degrades matrix to allow hatching. In worms and in flies, MMPs are regulated by the JNK pathway.
Matrix metalloproteinases (MMPs) are important for developmental tissue remodeling and for the inflammatory response. Although the vertebrate MMP family is large and functionally redundant, the fruitfly Drosophila melanogaster has only two MMPs, both essential genes. Our previous work demonstrated that Mmp1 is required for growth of the tracheal system, and we suggested that the mutant phenotype resulted from aberrant persistence of cell adhesion to the extracellular matrix. Here we report the identification of NijA, a transmembrane protein whose vertebrate homologs regulate cell adhesion, as a two-hybrid binding partner for Mmp1. The binding of Mmp1 and NijA was confirmed by coimmunoprecipitation of endogenous proteins from flies, and the endogenous proteins were found to colocalize at the tracheal cell surface in larvae. When NijA is expressed in S2 cells, they lose adhesion to surfaces; this adhesion-loss phenotype is dependent on the expression and catalytic activity of Mmp1. Our data indicate that Mmp1 releases the N-terminal extracellular domain of NijA. This liberated ectodomain promotes the loss of cell adhesion in a cell-nonautonomous manner. We suggest that tracheal cell adhesion is regulated by a novel mechanism utilizing an MMP and a ninjurin family member.
Tumor-necrosis factor (TNF), a pleiotropic cytokine, triggers physiological and pathological responses in several organs. Here we show that deletion of the mouse gene Timp3 resulted in an increase in TNF-alpha converting enzyme activity, constitutive release of TNF and activation of TNF signaling in the liver. The increase in TNF in Timp3(-/-) mice culminated in hepatic lymphocyte infiltration and necrosis, features that are also seen in chronic active hepatitis in humans. This pathology was prevented when deletion of Timp3 was combined with Tnfrsf1a deficiency. In a liver regeneration model that requires TNF signaling, Timp3(-/-) mice succumbed to liver failure. Hepatocytes from Timp3(-/-) mice completed the cell cycle but then underwent cell death owing to sustained activation of TNF. This hepatocyte cell death was completely rescued by a neutralizing antibody to TNF. Dysregulation of TNF occurred specifically in Timp3(-/-), and not Timp1(-/-) mice. These data indicate that TIMP3 is a crucial innate negative regulator of TNF in both tissue homeostasis and tissue response to injury.
The ovary and uterus undergo extensive tissue remodeling throughout each reproductive cycle. This remodeling of the extracellular environment is dependent upon the cyclic hormonal changes associated with each estrous or menstrual cycle. In the ovary, tissue remodeling is requisite for growth and expansion of the follicle, breakdown of the follicular wall during the ovulatory process, transformation of the postovulatory follicle into the corpus luteum, as well as the structural dissolution of the corpus luteum during luteal regression. In the uterus, there is extraordinary turnover of the endometrial connective tissue matrix during each menstrual cycle. This turnover encompasses the complete breakdown and loss of this layer, followed by its subsequent regrowth. With implantation, extensive remodeling of the uterus occurs to support placentation. These dynamic changes in the ovarian and uterine extracellular architecture are regulated, in part, by the matrix metalloproteinase (MMP) system. The MMP system acts to control connective tissue remodeling processes throughout the body and is comprised of both a proteolytic component, the MMPs, and a regulatory component, the associated tissue inhibitors of metalloproteinases. The current review will highlight the key features of the MMPs and tissue inhibitors of metalloproteinases, focus on the changes and regulation of the MMP system that take place throughout the estrous and menstrual cycles, and address the impact of the dynamic tissue remodeling processes on ovarian and uterine physiology.