Connecting beta2-adrenergic receptor to the actin cytoskeleton and inhibiting microtubule polymerization: EBP50/NHERF, ilimaquinone, and Op18/stathmin.
Description
- Language(s)
-
English
- Published
-
2005.
- Summary
-
Both the actin and the microtubule cytoskeleton are involved in transporting transmembrane proteins through cells. Using fluorescent imaging of living cells, we have found that endocytosed beta2-adrenergic receptor enters membrane tubules that rapidly move along microtubules. Using epi-fluorescent and confocal microscopy, we have demonstrated that beta2-adrenergic receptor clustering, endocytosis, recycling, and entry into membrane tubules are sensitive to latrunculin. Using co-immunoprecipitation, we have discovered that EBP50/NHERF (50 kDa ERM-binding phosphoprotein/Na + -H + exchanger regulatory factor), a component of the apical actin cytoskeleton that binds to the beta2-adrenergic receptor in vitro , also binds to the beta2-adrenergic receptor in cells. This bound EBP50/NHERF is phosphorylated, and possibly exists as a homo-dimer in cells. Binding to EBP50/NHERF or a related protein--possibly in a larger complex that contains actin--may regulate beta2-adrenergic receptor trafficking in tissue culture cells. Microtubule arrays are established in cells by a number of stabilizing and destabilizing proteins. Microtubule associated proteins, or MAPs, are a class of microtubule stabilizing proteins. We identify a ~100 kDa factor that destabilizes microtubules by causing catastrophes in the presence of the drug, ilimaquinone. We also demonstrate that this factor is not a MAP. Op18 family members, which are also not MAPS, destabilize microtubules both by causing catastrophes and by sequestering tubulin subunits. Using video-enhanced DIC microscopy, we provide evidence that Op18 causes catastrophes at both ends of microtubules in vitro , indicating that Op8 disrupts protofilament packing. Furthermore, hydrodynamic analysis of Op18 in vitro and in vivo demonstrates that Op18 does not act as a microtubule sequestering protein in Xenopus egg extracts, but is found in a large complex of unknown composition in interphase extracts.
- Note
-
Adviser: Mark E. von Zastrow.
Source: Dissertation Abstracts International, Volume: 66-02, Section: B, page: 0656.
Also available online.
- Physical Description
-
xix, 225 p. :
col. ill. ;
28 cm
Viewability