Nuclear localization and molecular partners of BIG1, a brefeldin A-inhibited guanine nucleotide-exchange protein for ADP-ribosylation factors

Jang

et al. 2006

MBoC

Heat-shock protein 90 (Hsp90) is a molecular chaperone that plays a key role in the conformational maturation of various transcription factors and protein kinases in signal transduction. Multifunctional ribosomal protein S3 (rpS3), a component of the ribosomal small subunit, is involved in DNA repair and apoptosis. Our data show that Hsp90 binds directly to rpS3 and the functional consequence of Hsp90-rpS3 interaction results in the prevention of the ubiquitination and the proteasome-dependent degradation of rpS3, subsequently retaining the function and the biogenesis of the ribosome. Interference of Hsp90 activity by Hsp90 inhibitors appears to dissociate rpS3 from Hsp90, associate the protein with Hsp70, and induce the degradation of free forms of rpS3. Furthermore, ribosomal protein S6 (rpS6) also interacted with Hsp90 and exhibited a similar effect upon treatment with Hsp90 inhibitors. Therefore, we conclude that Hsp90 regulates the function of ribosomes by maintaining the stability of 40S ribosomal proteins such as rpS3 and rpS6.

Section: Purification Of Nucleolimentioning

confidence: 99%

Interaction of Hsp90 with Ribosomal Proteins Protects from Ubiquitination and Proteasome-dependent Degradation

Jang

et al. 2006

MBoC

Proc. Natl. Acad. Sci. U.S.A.

“…Boal and Stephens also reported that Golgi structure was altered after BIG1 depletion (19). In addition to its Golgi association, BIG1 was accumulated in nuclei of serum-deprived HepG2 cells (20) or after their incubation with the immunosuppressive FK506 (21) or 8-Br-cAMP (22). In other conditions, BIG2 was associated with the trans-Golgi network and recycling endosomes (17,23).…”

mentioning

confidence: 94%

Effects of brefeldin A-inhibited guanine nucleotide-exchange (BIG) 1 and KANK1 proteins on cell polarity and directed migration during wound healing

Li¹,

Kuo

Waterman‐Storer

et al. 2011

Self Cite

Brefeldin A-inhibited guanine nucleotide-exchange protein (BIG) 1 activates class I ADP ribosylation factors (ARFs) by accelerating the replacement of bound GDP with GTP to initiate recruitment of coat proteins for membrane vesicle formation. Among proteins that interact with BIG1, kinesin family member 21A (KIF21A), a plusend-directed motor protein, moves cargo away from the microtubule-organizing center (MTOC) on microtubules. Because KANK1, a protein containing N-terminal KN, C-terminal ankyrin-repeat, and intervening coiled-coil domains, has multiple actions in cells and also interacts with KIF21A, we explored a possible interaction between it and BIG1. We obtained evidence for a functional and physical association between these proteins, and found that the effects of BIG1 and KANK1 depletion on cell migration in woundhealing assays were remarkably similar. Treatment of cells with BIG1-or KANK1-specific siRNA interfered significantly with directed cell migration and initial orientation of Golgi/MTOC toward the leading edge, which was not mimicked by KIF21A depletion. Although colocalization of overexpressed KANK1 and endogenous BIG1 in HeLa cells was not clear microscopically, their reciprocal immunoprecipitation (IP) is compatible with the presence of small percentages of each protein in the same complexes. Depletion or overexpression of BIG1 protein appeared not to affect KANK1 distribution. Our data identify actions of both BIG1 and KANK1 in regulating cell polarity during directed migration; these actions are consistent with the presence of both BIG1 and KANK1 in dynamic multimolecular complexes that maintain Golgi/MTOC orientation, differ from those that might contain all three proteins (BIG1, KIF21A, and KANK1), and function in directed transport along microtubules.

Proc. Natl. Acad. Sci. U.S.A.

“…BIG1 had been localized at trans-Golgi structures (4,5); by electron microscopy, Golgi membranes in BIG1-depleted cells were less sharply defined and had more vesicle-like structures at the trans face than those in control or BIG2 siRNA-treated cells (6). BIG1 also was found in nuclei of serum-deprived HepG2 cells or after their brief incubation with the immunosuppressive drug FK506 (7) or with cAMP (8).…”

mentioning

confidence: 97%

Interaction of brefeldin A-inhibited guanine nucleotide-exchange protein (BIG) 1 and kinesin motor protein KIF21A

Shen

Meza-Carmen

Puxeddu

et al. 2008

Self Cite

. These newly recognized interactions of BIG1 and KIF21A should enable us to understand better the mechanisms through which, acting together, they may integrate local events in membrane trafficking with longer-range transport processes and to relate those processes to the diverse signaling and scaffold functions of BIG1.ADP-ribosylation factor 1 ͉ Golgi ͉ microtubule B refeldin A-inhibited guanine nucleotide-exchange protein (BIG) 1, a member of the Sec7 family of ADP-ribosylation factor (ARF) guanine nucleotide-exchange proteins (GEP), activates class I ARFs (human ARF1 and 3) by catalyzing replacement of ARF-bound GDP with GTP, to initiate membrane vesicle formation (1-3). BIG1 had been localized at trans-Golgi structures (4, 5); by electron microscopy, Golgi membranes in BIG1-depleted cells were less sharply defined and had more vesicle-like structures at the trans face than those in control or BIG2 siRNA-treated cells (6). BIG1 also was found in nuclei of serum-deprived HepG2 cells or after their brief incubation with the immunosuppressive drug FK506 (7) or with cAMP (8).In the ϳ 200-kDa BIG1 molecule, a central ARF-activating Sec7 domain was the first recognized functional structure (9). Elements identified later include a site in the N-terminal region that interacts with FK506-binding protein 13 (10) and an A kinase-anchoring protein sequence identical to one of three such sequences that differ in specificities for binding each of the four cAMP-dependent protein kinase regulatory (R) subunits and that were first identified in BIG2 (11), the very similar GEP initially co-purified with BIG1 (9). PKA-catalyzed phosphorylation of serine-883, a predicted substrate site in BIG1, was required for its cAMP-induced nuclear accumulation (8). Later experiments with recombinant proteins in vitro demonstrated that GEP activity of BIG1 was decreased after phosphorylation by PKA (12). Most recently, it was reported that BIG1, nucleolin, U3 small nucleolar RNA, the U3-binding protein fibrillarin, and the RNA-binding protein La may exist together in nuclear complexes, consistent with a potential role for BIG1 in nucleolar function (13). The C-terminal region of BIG1 includes a binding site for myosin IXb. This motor protein possesses GTPaseactivating protein activity for Rho that is inhibited by competition with RhoA for binding to myosin IXb (14).A role for myosin IXb in the translocation of BIG1 along actin fibers in cells remains to be demonstrated. We present here evidence that BIG1 interacts directly with the motor protein KIF21A, which is involved in its microtubule-dependent transport. KIF21A is a member of the family of kinesin proteins that control cell morphogenesis, survival, and other functions (15). The 45 KIF molecules are classified according to position of the motor domain as N-terminal, middle, and C-terminal types, respectively, N-, M-, and C-kinesins (16). KIF21A is an N-kinesin that acts as a plus-end-directed motor to move cargo away from the microtubule-organizing center. BIG1 activation of ARF1 also ...