The role of [beta]-transducin repeat-containing protein ([beta]-TrCP) in the regulation of NF-[kappa]B in vascular smooth muscle cells.
OBJECTIVE
Degradation of IkappaB is an essential step in nuclear factor (NF)-kappaB activation. However, the determinants regulating this process have not been defined in vascular smooth muscle cells (VSMCs). We hypothesized that the E3-ligase, beta-transducin repeat-containing protein 1 (beta-TrCP1), was a rate-determining mediator that regulates the ubiquitin-mediated degradation of IkappaBalpha (in VSMC).


RESULTS
Upregulation of beta-TrCP1 accelerated the rate of IkappaBalpha degradation, leading to increased NF-kappaB activity. In contrast, VSMCs harboring a dominant-negative beta-TrCP1 transgene lacking the F-box domain exhibited a reduction in serum-stimulated NF-kB activity but no alteration in response to tumor necrosis factor (TNF). These findings suggest that beta-TrCP1 increases the rate of NF-kappaB activation but is not rate-limiting in response to TNF in VSMCs. Endogenous beta-TrCP1 expression was regulated through the conserved Wnt cascade. Upregulation of Wnt1 resulted in beta-catenin-mediated activation of Tcf-4, leading to increased beta-TrCP1 expression and NF-kappaB activity. Furthermore, VSMCs harboring a Tcf-4 mutant lacking a beta-catenin binding domain exhibited a significant reduction in beta-TrCP1 expression along with abolishment of NF-kappaB activity.


CONCLUSIONS
We provide the first evidence of crosstalk between the Wnt cascade and NF-kappaB signaling in VSMCs. This crosstalk is mediated through the E3-ligase, beta-TrCP1.
Lillehei Heart Institute, Division of Cardiology, Department of Medicine, University of Minnesota, Minneapolis 55455, USA.
Xiaohong
X
Wang
Neeta
N
Adhikari
Qinglu
Q
Li
Zhanjun
Z
Guan
Jennifer L
JL
Hall
D000818:Animals; D001011:Aorta / Q000378:metabolism; D002478:Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D020672:I-kappa B Proteins / Q000235:genetics / Q000378:metabolism*; D007976:Leupeptins / Q000494:pharmacology; D018021:Lithium Chloride / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D015534:Trans-Activators / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D051153:Wnt Proteins; D051155:Wnt1 Protein; D029961:Zebrafish Proteins; D051176:beta Catenin; D044844:beta-Transducin Repeat-Containing Proteins / Q000235:genetics / Q000502:physiology*
C495270:CTNNB1 protein, human; C495268:Ctnnb1 protein, rat; D003598:Cytoskeletal Proteins; D020672:I-kappa B Proteins; D007976:Leupeptins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; C000606206:Nfkbia protein, rat; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D014409:Tumor Necrosis Factor-alpha; C495247:WNT1 protein, human; D051153:Wnt Proteins; D051155:Wnt1 Protein; C495245:Wnt1 protein, rat; D029961:Zebrafish Proteins; D051176:beta Catenin; D044844:beta-Transducin Repeat-Containing Proteins; D000072000:NF-KappaB Inhibitor alpha; D018021:Lithium Chloride; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde