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Title and Authors: The g-subunit of the coatomer
complex binds Cdc42 to
mediate transformation
Institutes Involved:

NCBI link: Mark Stamnes J. Cell. Bio.
Abstract: Cytoskeletal dynamics at the Golgi apparatus are regulated in part through a binding interaction between the Golgi-vesicle coat protein, coatomer, and the regulatory GTP-binding protein Cdc42 (Wu, W.J., J.W. Erickson, R. Lin, and R.A. Cerione. 2000. Nature. 405:800-804; Fucini, R.V., J.L. Chen, C. Sharma, M.M. Kessels, and M. Stamnes. 2002. Mol. Biol. Cell. 13:621-631). The precise role of this complex has not been determined. We have analyzed the protein composition of Golgi-derived coat protomer I (COPI)-coated vesicles after activating or inhibiting signaling through coatomer-bound Cdc42. We show that Cdc42 has profound effects on the recruitment of dynein to COPI vesicles. Cdc42, when bound to coatomer, inhibits dynein binding to COPI vesicles whereas preventing the coatomer-Cdc42 interaction stimulates dynein binding. Dynein recruitment was found to involve actin dynamics and dynactin. Reclustering of nocodazole-dispersed Golgi stacks and microtubule/dynein-dependent ER-to-Golgi transport are both sensitive to disrupting Cdc42 mediated signaling. By contrast, dynein-independent transport to the Golgi complex is insensitive to mutant Cdc42. We propose a model for how proper temporal regulation of motor-based vesicle translocation could be coupled to the completion of vesicle formation.


Introduction: ERGIC53 is a lectin, capable of binding mannose residues for return to the ER. CDC42 is a small GTPase with a C-terminal dilysine motif. CDC42 has various mutant forms that are either GTPase defective Cdc42Q61L, GTPase active, CDC42 contains an almost C-terminal Dilysine motif, Cdc42T17N nucleotide exchange defective mutant, \
constitutively active Cdc42 mutant that was fully GTPase-competent (Cdc42F28L)
Materials and Methods: pulldowns, heterologous expression, VSVG transport, endoglycosidase digestion assay,
Results: What are the main advancements in knowledge made in the paper, major findings: CDC42Q61L(ss) can bind other CDC42 effectors, but not COPI (gamma COPI), under high salt gamma COPI remains in the pulldown,
Discussion: How does this work add to or change the field or models being discussed?


What are the major flaws of this paper?
All dominant negative effects, COPI mutant did not effect VSVG forward traffic, retro traffic not tested

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TAEKLARDLKAVKYVECSALTQRGLKNVFDEAILAALEPPETQPKRKCCIF=cdc42