Project description:Autophagy is a catabolic membrane trafficking process involved in degradation of cellular constituents through lysosomes, which maintains cell and tissue homeostasis. While much attention has been focused on autophagic turnover of cytoplasmic materials, little is known regarding the role of autophagy in degrading nuclear components. Here we report that autophagy machinery mediates degradation of nuclear lamina in mammalian cells, a process we term laminophagy. The autophagy protein LC3 is present in the nucleus and directly interacts with the nuclear lamina protein Lamin B1, and associates with lamin-associated domains (LADs) on chromatin. This interaction does not downregulate Lamin B1 during starvation, but mediates nuclear lamina degradation upon tumorigenic insults, such as by oncogenic Ras. Laminophagy is achieved by nucleus-to-cytosol transport that delivers Lamin B1 to lysosome for degradation. Inhibiting autophagy or LC3-Lamin B1 interaction prevents oncogenic Ras-induced Lamin B1 loss and delays oncogene-induced cell cycle arrest. Our study unveils a role of autophagy in degrading nuclear materials, and suggests laminophagy as a guarding mechanism protecting cells from tumorigenesis.
Project description:Soil humic substances are known to positively influence plant growth and nutrition. In particular, low-molecular fractions have been shown to increase NO3- uptake and PM H+-ATPase activity and alter expression of related genes. Changes in maize root transcriptome due to treatment with nitrate (NO3-), Water-Extractable Humic Substances (WEHS) and NO3-+WEHS were analyzed.
Project description:Bone remodeling is a tightly regulated process that engages degradation and biogenesis of the bone matrix. The process is controlled by two major cell types, bone forming cells-osteoblasts and bone-degrading cells-osteoclasts. We are interested in the bone-resorption mechanism mediated by osteoclasts and wish to identify glycosylation genes that are regulated during the formation of osteoclast cells and determine the function of glycosylation and glycan-binding proteins in the osteoclastogenesis.
Project description:Physiologic turnover of interstitial collagen is mediated by a sequential pathway, in which collagen is fragmented by pericellular collagenases, endocytosed by specific collagen receptors, and routed to lysosomes for degradation by lysosomal cathepsins. Here, we used intravital microscopy to investigate if malignant tumors, which are characterized by high rates of extracellular matrix turnover, utilize a similar collagen degradation pathway. Tumors of epithelial, mesenchymal, or neural crest origin all displayed vigorous endocytic collagen degradation with an abundance of cells engaged in this process. These cells were identified as tumor-associated macrophage (TAM)-like cells that degraded collagen in a mannose receptor-dependent manner. Accordingly, increased intra-tumoral collagen was observed in mannose receptor-deficient mice. Whole transcriptome profiling uncovered a distinct extracellular matrix-catabolic signature of these collagen-degrading TAMs. Lineage-ablation studies revealed that collagen-degrading TAMs originated from circulating CCR2+ monocytes. The study identifies a novel function of TAMs in altering the tumor microenvironment through endocytic collagen turnover and establishes macrophages as centrally engaged in tumor-associated collagen degradation.