Re-evaluating the roles of myosin 18A[alpha] and F-actin in determining Golgi morphology

The peri-centrosomal localization and morphology of the Golgi apparatus depends largely on the microtubule cytoskeleton and the microtubule motor protein dynein. Recent studies proposed that myosin 18A[alpha] (M18A[alpha]) also contributes to Golgi morphology by binding the Golgi protein GOLPH3 and...

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Bibliographic Details
Published in:Cytoskeleton (Hoboken, N.J.) N.J.), 2017-05, Vol.74 (5), p.205
Main Authors: Bruun, Kyle, Beach, Jordan R, Heissler, Sarah M, Remmert, Kirsten, Sellers, James R, Hammer, John A
Format: Article
Language:English
Subjects:
Actin
Adenosine triphosphatase
Antibodies
Cell lines
Cell size
Cytology
Cytoskeleton
Dynein
Filaments
Golgi cells
Localization
Morphology
Motor activity
Motor task performance
Myosin
Nuclei
Walking
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Summary:The peri-centrosomal localization and morphology of the Golgi apparatus depends largely on the microtubule cytoskeleton and the microtubule motor protein dynein. Recent studies proposed that myosin 18A[alpha] (M18A[alpha]) also contributes to Golgi morphology by binding the Golgi protein GOLPH3 and walking along adjacent actin filaments to stretch the Golgi into its classic ribbon structure. Biochemical analyses have shown, however, that M18A is not an actin-activated ATPase and lacks motor activity. Our goal, therefore, was to define the precise molecular mechanism by which M18A[alpha] determines Golgi morphology. We show that purified M18A[alpha] remains inactive in the presence of GOLPH3, arguing against the Golgi-specific activation of the myosin. Using M18A-specific antibodies and expression of GFP-tagged M18A[alpha], we find no evidence that it localizes to the Golgi. Moreover, several cell lines with reduced or eliminated M18A[alpha] expression exhibited normal Golgi morphology. Interestingly, actin filament disassembly resulted in a marked reduction in lateral stretching of the Golgi in both control and M18A[alpha]-deficient cells. Importantly, this reduction was accompanied by an expansion of the Golgi in the vertical direction, vertical movement of the centrosome, and increases in the height of both the nucleus and the cell. Collectively, our data indicate that M18A[alpha] does not localize to the Golgi or play a significant role in determining its morphology, and suggest that global F-actin disassembly alters Golgi morphology indirectly by altering cell shape.
ISSN:1949-3584
1949-3592
DOI:10.1002/cm.21364