Understanding how cells invade through basement membrane in vivo

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PROJECT SUMMARY Basement membrane (BM) is a dense, sheet-like extracellular matrix that surrounds most tissues. During development and immune cell trafficking, specialized cells acquire the unique ability to breach BM barriers to disperse, construct tissues, and migrate to sites of infection and injury. Cell invasion is also inappropriately initiated during numerous diseases and underlies tissue destruction in asthma, stroke, arthritis, multiple sclerosis, and metastatic cancer. Understanding how cells traverse BM barriers is thus of fundamental importance in improving human health. Cell invasion events are often stochastic, rapid, and involve dynamic adhesions and communication between the invading cell, the BM, and the neighboring tissues. Owing to this complexity, it is not possible to faithfully recapitulate cell invasion with in vitro assays, and it has been difficult to visualize and genetically dissect invasion in vertebrate tissues. As a result, the mechanisms underlying cell invasive behavior remain poorly understood. Anchor cell invasion in C. elegans is a highly stereotyped in vivo model of cell invasion that uniquely combines many powerful experimental approaches including subcellular visual analysis of cell-BM interactions, molecular activity sensors, rapid genome editing, cell-type specific gene manipulation, and powerful forward genetic and functional genomic approaches. Using these strengths, this study will characterize how invading cells acquire and use energy to fuel BM invasion. This work will reveal mechanisms that direct polarized glucose import and the construction of specialized electron transport chain enriched mitochondria that provide localized ATP to power the BM breaching machinery. Further, the outlined experiments will determine how lipid biosynthesis is integrated into a conserved cell invasion transcriptional program and how lipid producing enzymes, which are overexpressed in most metastatic cancers, build a large, transient, invasive protrusion that opens paths through BM barriers. The proposed study will also elucidate how invasive cells adapt their invasion program to the absence of matrix metalloproteinases (MMPs) by physically displacing the BM, which will inform more effective approaches to block invasion with MMP inhibitors that have thus far failed to be effective in clinical trials. Finally, this work will identify molecular mechanisms that prevent and heal plasma membrane damage during BM breaching, thus revealing mechanisms that could be exploited to target cells in the act of invading. These integrative studies spanning cellular energetics, extracellular matrix, transcriptional regulation, and membrane dynamics are relevant to the NIH’s mission as they will lead to a deeper understanding of the fundamental biological process of cell invasive behavior, thus allowing for the development of better therapeutic strategies to modulate invasion in human disease.