Altman:Research

Department of Physics, Willamette University

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Single molecule studies of Acanthamoeba myosin 1

We are examining the force-sensitivity of Acanthamoeba myosin 1c (AM1C) activity. Class 1 myosins have been split into two subclasses. While subclass 2 myosins are hypothesized to have a force-dependent activity, subclass 1 myosins are not. Two subclass 2 myosins (Rat Myo1b and Mouse Myo1c) have been shown to have a high degree of force-sensitivity, but no subclass 1 myosin has yet been tested. To test the force sensitivity of AM1C, which is from subclass 1, we are using an optical trap, which allows us to apply picoNewton forces to single myosin motors.

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  Cartoon of a myosin attached to a bead that is held in an optical trap.

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  Image taken from De La Cruz, et al.

Retinal pigment epithelium phagocytosis

Retinal pigment epithelium (RPE) cells phagocytose waste shed by rod photoreceptor cells. This is important for the health of the eye, and failure to complete this process results in retinal degeneration. We study the role of molecular motors in this process. Specifically, we are testing the hypothesis that motor proteins myosin VI and VIIa generate the forces and motion required for the internalization of rod cell debris. To do this, we observe internalization of micron-sized microspheres by a primary RPE cell line (ARPE-19). To perturb the function of a particular myosin, we over-express myosins lacking the motor domain.

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  Overlay of a DIC and fluorescence image of an ARPE-19 cell internalizing microspheres while transiently over-expressing a GFP-tagged myosin

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  Tracking a 1-micron-diameter microsphere that has been internalized by an ARPE-19 cell.