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Vol. 19, Issue 12, 5156-5167, December 2008

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The C-Terminal Tail Region of Nonmuscle Myosin II Directs Isoform-specific Distribution in Migrating Cells

Department of Pharmacology and Cancer Biology, Duke University Medical Center; Durham, NC 27710

Submitted May 29, 2008; Revised September 19, 2008; Accepted September 30, 2008
Monitoring Editor: Yu-Li Wang

Nonmuscle myosin II isoforms A and B (hereafter, IIA and IIB) perform unique roles in cell migration, even though both isoforms share the same basic molecular functions. That IIA and IIB assume distinct subcellular distribution in migrating cells suggests that discrete spatiotemporal regulation of each isoform's activity may provide a basis for its unique migratory functions. Here, we make the surprising finding that swapping a small C-terminal portion of the tail between IIA and IIB inverts the distinct distribution of these isoforms in migrating cells. Moreover, swapping this region between isoforms also inverts their specific turnover properties, as assessed by fluorescence recovery after photobleaching and Triton solubility. These data, acquired through the use of chimeras of IIA and IIB, suggest that the C-terminal region of the myosin heavy chain supersedes the distinct motor properties of the two isoforms as the predominant factor directing isoform-specific distribution. Furthermore, our results reveal a correlation between isoform solubility and distribution, leading to the proposal that the C-terminal region regulates isoform distribution by tightly controlling the amount of each isoform that is soluble and therefore available for redistribution into new protrusions.

* Present address: Department of Zoology, University of Wisconsin, Madison, WI 53706.

Address correspondence to: Anthony R. Means (means001{at}mc.duke.edu)

Abbreviations used: IIA and IIB, nonmuscle myosin II isoforms A and B; ACD, assembly competent domain; FRAP, fluorescence recovery after photobleaching; mChe, mCherry; NHT, nonhelical tailpiece; ROCK, Rho kinase; RLC, myosin regulatory light chain; TX-100, Triton X-100.