Intracellular transport is ubiquitous in animal cells and has fundamental importance for diverse biological phenomena, such as secretion, neuronal signaling, organization of endomembranes, and mitosis. The driving force for intracellular transport is provided by molecular motors bound to the surface of cargo organelles and moving along microtubules (MTs) and actin filaments (AFs). Switching between these two types of transport must be precisely regulated for the delivery of organelles to specific regions of the cytoplasm. However, the mechanisms of such regulation remain a mystery. Here, we propose to answer the question about the regulation of switching between MTs and AFs using Xenopus melanophores as an experimental system. These cells rapidly redistribute in the cytoplasm thousands of membrane-bounded pigment granules, which aggregate in the cell center or disperse throughout the cytoplasm by means of pigment granule-bound molecular motors that use both MT and AF tracks. Switching of pigment granules between MTs and AFs is controlled by the levels of the second messenger cAMP. Background data by the principal investigator suggest that switching between the two types of tracks is based on a continuous tug-of-war between transport systems. The outcome of the tug-of-war is decided by the relative activities of MT-based and AF-based molecular motors simultaneously bound to the same pigment granule. Preliminary data also indicate that besides molecular motors, organelle transport and its switching between MT and AF tracks involves additional proteins that regulate docking of organelles to the destination track. This proposal will use molecular, cellular, and biochemical approaches to test the hypothesis that aggregation and dispersion signals regulate organelle docking and activities of granule-bound molecular motors through interconnected mechanisms that generate distinct kinetics of transferring pigment granules between MTs and AFs during aggregation and dispersion. To examine these regulatory mechanisms, docking molecules will be identified, and the regulation of their binding to transport tracks and pigment granules will be elucidated. The role of phosphorylation of subunits of molecular motors in regulation of their activities will be also determined.
The goal of this proposal is an understanding of how membrane organelles switch between the two types of cytoskeletal transport tracks, microtubules and actin filaments. Such switching is a critical part of the intracellular transport process, which is essential for normal cell function. Defects in intracellular transport are responsible for many human diseases and our understanding of the molecular basis of these defects is paving the way to future effective therapeutics of diseases such as cancer, diabetes/Wolcott- rallison syndrome, and neurodegenerative disorders including Alzheimer and Huntington diseases.
|Deb Roy, Abhijit; Yin, Taofei; Choudhary, Shilpa et al. (2017) Optogenetic activation of Plexin-B1 reveals contact repulsion between osteoclasts and osteoblasts. Nat Commun 8:15831|
|Semenova, Irina; Gupta, Dipika; Usui, Takeo et al. (2017) Stimulation of microtubule-based transport by nucleation of microtubules on pigment granules. Mol Biol Cell 28:1418-1425|
|Marchenko, Olena O; Das, Sulagna; Yu, Ji et al. (2017) A minimal actomyosin-based model predicts the dynamics of filopodia on neuronal dendrites. Mol Biol Cell 28:1021-1033|
|Rezaul, Karim; Gupta, Dipika; Semenova, Irina et al. (2016) Engineered Tug-of-War Between Kinesin and Dynein Controls Direction of Microtubule Based Transport In Vivo. Traffic 17:475-86|
|Osunbayo, Olaolu; Butterfield, Jacqualine; Bergman, Jared et al. (2015) Cargo transport at microtubule crossings: evidence for prolonged tug-of-war between kinesin motors. Biophys J 108:1480-3|
|Semenova, Irina; Ikeda, Kazuho; Resaul, Karim et al. (2014) Regulation of microtubule-based transport by MAP4. Mol Biol Cell 25:3119-32|
|Denton, Kyle R; Lei, Ling; Grenier, Jeremy et al. (2014) Loss of spastin function results in disease-specific axonal defects in human pluripotent stem cell-based models of hereditary spastic paraplegia. Stem Cells 32:414-23|
|Schroeder 3rd, Harry W; Hendricks, Adam G; Ikeda, Kazuho et al. (2012) Force-dependent detachment of kinesin-2 biases track switching at cytoskeletal filament intersections. Biophys J 103:48-58|
|Ikeda, Kazuho; Zhapparova, Olga; Brodsky, Ilya et al. (2011) CK1 activates minus-end-directed transport of membrane organelles along microtubules. Mol Biol Cell 22:1321-9|
|Lomakin, Alexis J; Kraikivski, Pavel; Semenova, Irina et al. (2011) Stimulation of the CLIP-170--dependent capture of membrane organelles by microtubules through fine tuning of microtubule assembly dynamics. Mol Biol Cell 22:4029-37|
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