Localization of the rat myosin I molecules myr 1 and myr 2 and in vivo targeting of their tail domains

Abstract

Myr 1 is a widely distributed mammalian myosin I molecule related to brush border myosin 1. A second widely distributed myosin I molecule similar to myr 1 and brush border myosin I, called myr 2, has now been identified. Specific antibodies and expression of epitope-tagged molecules were used to determine the subcellular localization of myr 1 and myr 2 in NRK cells. Myr 1 was detected at the plasma membrane and was particularly enriched in cell protrusions like lamellipodia, membrane ruffles and filopodia. In dividing cells myr 1 localized to the cleavage furrow. Myr 2 was localized in a discrete punctate pattern in resting cells and in cells undergoing cytokinesis. In subcellular fractionation experiments myr 1 and myr 2 were both partly soluble and partly associated with smooth membranes of medium density. The tail domains of myosin I molecules have been proposed to interact with a receptor and thereby determine the subcellular localization. To test this hypothesis we expressed the tail domains of myr 1 and myr 2 that lack the F-actin-binding myosin head domain in NRK cells. These tail domains also partly copurified with smooth membranes of medium density and immunolocalized similar to the respective endogenous myosin I; however, they exhibited a lower affinity for membranes and an increased diffuse cytosolic localization. These results suggest that the tail domains of myr 1 and myr 2 are sufficient for subcellular targeting but that their head domains also contribute significantly to maintaining a proper subcellular localization.

mDia1 Assembles a Linear F-Actin Coat at Membrane Invaginations To Drive Listeria monocytogenes Cell-to-Cell Spreading

“…S5D ). In line with the reported localization of Myo1c to the plasma membrane and actin-rich membrane structures ( 53 , 54 , 57 – 62 ), we observed elevated levels of Myo1c-GFP at the plasma membrane surrounding L. monocytogenes membrane protrusions ( Fig. S5E ).…”

A Hearing Loss-Associated myo1c Mutation (R156W) Decreases the Myosin Duty Ratio and Force Sensitivity

“…Interestingly, this switch II mutation also results in the improper localization of the protein. Given the importance of the motor domain in myosin I localization , , it will be important to determine if the R156W mutation in myo1c also has an effect on the subcellular localization of this molecular motor.…”

Calcium Regulation of Calmodulin Binding to and Dissociation from the Myo1c Regulatory Domain

“…Given the localization of myo1c to membranes in dynamic regions of the cell (3,21,22), it is likely that myo1c experiences transient changes of calcium concentration within a range that is capable of regulating motor activity. Indeed, it has been proposed that calcium regulates the fast-adaptation response in sensory hair cells (23) by binding directly to myo1c-bound calmodulin.…”