Gelfand Lab  
  at Northwestern University - Chicago, IL  
     
     
     
    Regulation of Organelle Transport    
    In Xenopus Melanophores    
     
    Pigment cells, known as melanophores, from the African clawed frog, Xenopus leavis, provide an excellent model system for the study of organelle transport. Melanophores contain membrane bound organelles, known as melanosomes, which are filled with the pigment, melanin. Melanophores function to change the color of the skin. When pigment is clustered in the perinuclear region most of the the cytoplasm is transparent and the skin has light color. Dispersion of pigment makes makes the cytoplasm (and therefore the skin) look dark. Cells aggregate or disperse melanosomes in response to hormonal signals (melatonin and melanocyte-stimulating hormon, respectively).    
     
    Our lab has previously identified that the outward movements (dispersion) of melanosomes are powered by kinesin-2 and myosin Va, whereas the inward movements (aggregation) are powered by cytoplasmic dynein. We have also demonstrated that signaling cascade by hormone receptors act through the level of cAMP, and activity of protein kinase A (PKA) dictates the dispersion and aggregation phenotypes for melanosomes. Thus, pigment cells provide an outstanding system to study organelle transport. Furthermore, we believe that the key properties of this system, such as the presence of three types of molecular motors and their concerted action in the movement/anchoring of membrane organelles, are shared by most other systems of organelle transport.    
     
    We are currently investigating the mechanisms for regulating the activities of molecular motors by PKA and for coordinating the action of plus- and minus-end-directed microtubule motors.    
     
     
     
     
    This movie shows pigment oganelles (melanosomes)
moving along microtubules during dispersion.		    
     
     
     
 
Last updated on January 8, 2008
  
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