Targeting of a tropomyosin isoform to short microfilaments associated with the Golgi complex.

Justin M Percival, Julie A I Hughes, Darren L Brown, Galina Schevzov, Kirsten Heimann, Bernadette Vrhovski, Nicole Bryce, Jennifer L Stow, Peter W Gunning

Oncology Research Unit, The Children's Hospital at Westmead, Westmead, NSW 2145, Australia.

Molecular biology of the cell 2004 Jan

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A growing body of evidence suggests that the Golgi complex contains an actin-based filament system. We have previously reported that one or more isoforms from the tropomyosin gene Tm5NM (also known as gamma-Tm), but not from either the alpha- or beta-Tm genes, are associated with Golgi-derived vesicles (Heimann et al., (1999). J. Biol. Chem. 274, 10743-10750). We now show that Tm5NM-2 is sorted specifically to the Golgi complex, whereas Tm5NM-1, which differs by a single alternatively spliced internal exon, is incorporated into stress fibers. Tm5NM-2 is localized to the Golgi complex consistently throughout the G1 phase of the cell cycle and it associates with Golgi membranes in a brefeldin A-sensitive and cytochalasin D-resistant manner. An actin antibody, which preferentially reacts with the ends of microfilaments, newly reveals a population of short actin filaments associated with the Golgi complex and particularly with Golgi-derived vesicles. Tm5NM-2 is also found on these short microfilaments. We conclude that an alternative splice choice can restrict the sorting of a tropomyosin isoform to short actin filaments associated with Golgi-derived vesicles. Our evidence points to a role for these Golgi-associated microfilaments in vesi cle budding at the level of the Golgi complex.

Citation

Justin M Percival, Julie A I Hughes, Darren L Brown, Galina Schevzov, Kirsten Heimann, Bernadette Vrhovski, Nicole Bryce, Jennifer L Stow, Peter W Gunning. Targeting of a tropomyosin isoform to short microfilaments associated with the Golgi complex. Molecular biology of the cell. 2004 Jan;15(1):268-80