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Updated: Mar 26, 2026
Myosin-Specific Adaptations of In vitro Fluorescence Microscopy-Based Motility Assays
Published on: February 4, 2021
Selective localization of myosin-I proteins in macropinosomes and actin waves
Hanna Brzeska1, Hilary Koech1, Kevin J Pridham1
1Laboratory of Cell Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland.
Abstract:
Class I myosins are widely expressed with roles in endocytosis and cell migration in a variety of cell types. Dictyostelium express multiple myosin Is, including three short-tailed (Myo1A, Myo1E, Myo1F) and three long-tailed (Myo1B, Myo1C, Myo1D). Here we report the molecular basis of the specific localizations of short-tailed Myo1A, Myo1E, and Myo1F compared to our previously determined localization of long-tailed Myo1B. Myo1A and Myo1B have common and unique localizations consistent with the various features of their tail region; specifically the BH sites in their tails are required for their association with the plasma membrane and heads are sufficient for relocalization to the front of polarized cells. Myo1A does not localize to actin waves and macropinocytic protrusions, in agreement with the absence of a tail region which is required for these localizations of Myo1B. However, in spite of the overall similarity of their domain structures, the cellular distributions of Myo1E and Myo1F are quite different from Myo1A. Myo1E and Myo1F, but not Myo1A, are associated with macropinocytic cups and actin waves. The localizations of Myo1E and Myo1F in macropinocytic structures and actin waves differ from the localization of Myo1B. Myo1B colocalizes with F-actin in the actin waves and at the tips of mature macropinocytic cups whereas Myo1E and Myo1F are in the interior of actin waves and along the entire surface of macropinocytic cups. Our results point to different mechanisms of targeting of short- and long-tailed myosin Is, and are consistent with these myosins having both shared and divergent cellular functions.
Insights
Short-tailed myosins (Myo1A, Myo1E, Myo1F) in Dictyostelium exhibit distinct localizations compared to long-tailed Myo1B. Tail regions influence plasma membrane association and localization to actin waves and macropinocytic structures, revealing diverse myosin functions.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Class I myosins are crucial for cellular processes like endocytosis and migration.
- Dictyostelium discoideum possess multiple Class I myosins, including short-tailed (Myo1A, Myo1E, Myo1F) and long-tailed (Myo1B, Myo1C, Myo1D) isoforms.
Purpose of the Study:
- To elucidate the molecular basis for the specific cellular localizations of short-tailed myosins (Myo1A, Myo1E, Myo1F).
- To compare these localizations with the previously determined localization of long-tailed Myo1B.
- To understand how tail region features dictate myosin targeting and function.
Main Methods:
- Localization studies of Dictyostelium myosin I isoforms.
- Analysis of specific domains, such as the BH sites in the tail region.
- Comparison of localization patterns in relation to cellular structures like actin waves and macropinocytic cups.
Main Results:
- Myosin 1A (Myo1A) and Myosin 1B (Myo1B) share common and unique localizations, with tail regions, particularly BH sites, mediating plasma membrane association.
- Myosin heads alone are sufficient for relocalization to the leading edge of polarized cells.
- Myosin 1E (Myo1E) and Myosin 1F (Myo1F) associate with macropinocytic cups and actin waves, unlike Myo1A, but display different localization patterns within these structures compared to Myo1B.
Conclusions:
- The tail regions of Class I myosins play critical roles in their specific cellular targeting and functions.
- Short-tailed and long-tailed myosins exhibit distinct localization mechanisms and potentially divergent cellular roles.
- Myosin localization patterns are consistent with their involvement in shared and unique cellular processes such as endocytosis and cell migration.
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