Limits...
Vesicles carry most exocyst subunits to exocytic sites marked by the remaining two subunits, Sec3p and Exo70p.

Boyd C, Hughes T, Pypaert M, Novick P - J. Cell Biol. (2004)

Bottom Line: We have used photobleaching recovery experiments to characterize the dynamic behavior of the eight subunits that make up the exocyst.One subset (Sec5p, Sec6p, Sec8p, Sec10p, Sec15p, and Exo84p) exhibits mobility similar to that of the vesicle-bound Rab family protein Sec4p, whereas Sec3p and Exo70p exhibit substantially more stability.Disruption of actin assembly abolishes the ability of the first subset of subunits to recover after photobleaching, whereas Sec3p and Exo70p are resistant.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520, USA.

ABSTRACT
Exocytosis in the budding yeast Saccharomyces cerevisiae occurs at discrete domains of the plasma membrane. The protein complex that tethers incoming vesicles to sites of secretion is known as the exocyst. We have used photobleaching recovery experiments to characterize the dynamic behavior of the eight subunits that make up the exocyst. One subset (Sec5p, Sec6p, Sec8p, Sec10p, Sec15p, and Exo84p) exhibits mobility similar to that of the vesicle-bound Rab family protein Sec4p, whereas Sec3p and Exo70p exhibit substantially more stability. Disruption of actin assembly abolishes the ability of the first subset of subunits to recover after photobleaching, whereas Sec3p and Exo70p are resistant. Immunogold electron microscopy and epifluorescence video microscopy indicate that all exocyst subunits, except for Sec3p, are associated with secretory vesicles as they arrive at exocytic sites. Assembly of the exocyst occurs when the first subset of subunits, delivered on vesicles, joins Sec3p and Exo70p on the plasma membrane. Exocyst assembly serves to both target and tether vesicles to sites of exocytosis.

Show MeSH

Related in: MedlinePlus

Model of targeting and tethering in S. cerevisiae. The exocyst subunits (except for Sec3p) associate with vesicles before movement to the bud tip. Once the vesicle has arrived at the bud tip, Sec3p and Exo70p bind to the rest of the exocyst to complete the formation of the tethering complex. Exo70p is also found to ride vesicles to sites of exocytosis in addition to localizing there by interacting with Rho3p.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2172445&req=5

fig8: Model of targeting and tethering in S. cerevisiae. The exocyst subunits (except for Sec3p) associate with vesicles before movement to the bud tip. Once the vesicle has arrived at the bud tip, Sec3p and Exo70p bind to the rest of the exocyst to complete the formation of the tethering complex. Exo70p is also found to ride vesicles to sites of exocytosis in addition to localizing there by interacting with Rho3p.

Mentions: In total, our data support a model in which a subset of subunits is delivered on vesicles and exocyst assembly is completed only as the vesicles arrive at sites of exocytosis marked by the remaining subunits, Sec3p and Exo70p (Fig. 8). An important implication of this model is that there must be a cycle of assembly for the exocyst. If we consider the cycle to begin with exocyst assembly and vesicle tethering, then a mechanism must exist for disassembly and recycling of the exocyst subunits (apart from Sec3p). We presently have no information on the mechanisms of disassembly and recycling. There must also be a mechanism for recruiting certain members of the exocyst onto newly formed, or forming, secretory vesicles. It has been speculated that exocyst components are loaded onto vesicles at the trans-Golgi (Munro, 2004), but this has yet to be shown experimentally.


Vesicles carry most exocyst subunits to exocytic sites marked by the remaining two subunits, Sec3p and Exo70p.

Boyd C, Hughes T, Pypaert M, Novick P - J. Cell Biol. (2004)

Model of targeting and tethering in S. cerevisiae. The exocyst subunits (except for Sec3p) associate with vesicles before movement to the bud tip. Once the vesicle has arrived at the bud tip, Sec3p and Exo70p bind to the rest of the exocyst to complete the formation of the tethering complex. Exo70p is also found to ride vesicles to sites of exocytosis in addition to localizing there by interacting with Rho3p.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172445&req=5

fig8: Model of targeting and tethering in S. cerevisiae. The exocyst subunits (except for Sec3p) associate with vesicles before movement to the bud tip. Once the vesicle has arrived at the bud tip, Sec3p and Exo70p bind to the rest of the exocyst to complete the formation of the tethering complex. Exo70p is also found to ride vesicles to sites of exocytosis in addition to localizing there by interacting with Rho3p.
Mentions: In total, our data support a model in which a subset of subunits is delivered on vesicles and exocyst assembly is completed only as the vesicles arrive at sites of exocytosis marked by the remaining subunits, Sec3p and Exo70p (Fig. 8). An important implication of this model is that there must be a cycle of assembly for the exocyst. If we consider the cycle to begin with exocyst assembly and vesicle tethering, then a mechanism must exist for disassembly and recycling of the exocyst subunits (apart from Sec3p). We presently have no information on the mechanisms of disassembly and recycling. There must also be a mechanism for recruiting certain members of the exocyst onto newly formed, or forming, secretory vesicles. It has been speculated that exocyst components are loaded onto vesicles at the trans-Golgi (Munro, 2004), but this has yet to be shown experimentally.

Bottom Line: We have used photobleaching recovery experiments to characterize the dynamic behavior of the eight subunits that make up the exocyst.One subset (Sec5p, Sec6p, Sec8p, Sec10p, Sec15p, and Exo84p) exhibits mobility similar to that of the vesicle-bound Rab family protein Sec4p, whereas Sec3p and Exo70p exhibit substantially more stability.Disruption of actin assembly abolishes the ability of the first subset of subunits to recover after photobleaching, whereas Sec3p and Exo70p are resistant.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520, USA.

ABSTRACT
Exocytosis in the budding yeast Saccharomyces cerevisiae occurs at discrete domains of the plasma membrane. The protein complex that tethers incoming vesicles to sites of secretion is known as the exocyst. We have used photobleaching recovery experiments to characterize the dynamic behavior of the eight subunits that make up the exocyst. One subset (Sec5p, Sec6p, Sec8p, Sec10p, Sec15p, and Exo84p) exhibits mobility similar to that of the vesicle-bound Rab family protein Sec4p, whereas Sec3p and Exo70p exhibit substantially more stability. Disruption of actin assembly abolishes the ability of the first subset of subunits to recover after photobleaching, whereas Sec3p and Exo70p are resistant. Immunogold electron microscopy and epifluorescence video microscopy indicate that all exocyst subunits, except for Sec3p, are associated with secretory vesicles as they arrive at exocytic sites. Assembly of the exocyst occurs when the first subset of subunits, delivered on vesicles, joins Sec3p and Exo70p on the plasma membrane. Exocyst assembly serves to both target and tether vesicles to sites of exocytosis.

Show MeSH
Related in: MedlinePlus