TY - JOUR
T1 - Role of protein kinase C and NF-κB in proteolysis-inducing factor-induced proteasome expression in C2C12 myotubes
AU - Smith, H. J.
AU - Wyke, S. M.
AU - Tisdale, M. J.
PY - 2004/5/4
Y1 - 2004/5/4
N2 - Proteolysis-inducing factor (PIF) is a sulphated glycoprotein produced by cachexia-inducing tumours, which initiates muscle protein degradation through an increased expression of the ubiquitin-proteasome proteolytic pathway. The role of kinase C (PKC) in PIF-induced proteasome expression has been studied in murine myotubes as a surrogate model of skeletal muscle. Proteasome expression induced by PIF was attenuated by 4α-phorbol 12-myristate 13-acetate (100 nM) and by the PKC inhibitors Ro31-8220 (10 μM), staurosporine (300 nM), calphostin C (300 nM) and Gö 6976 (200 μM). Proteolysis-inducing factor-induced activation of PKCα, with translocation from the cytosol to the membrane at the same concentration as that inducing proteasome expression, and this effect was attenuated by calphostin C. Myotubes transfected with a constitutively active PKCα (pCO2) showed increased expression of proteasome activity, and a longer time course, compared with their wild-type counterparts. In contrast, myotubes transfected with a dominant-negative PKCα (pKSI), which showed no activation of PKCα in response to PIF, exhibited no increase in proteasome activity at anytime point. Proteolysis-inducing factor-induced proteasome expression has been suggested to involve the transcription factor nuclear factor-κB (NF-κB), which may be activated through PKC. Proteolysis-inducing factor induced a decrease in cytosolic 1-κBα and an increase in nuclear binding of NF-κB in pCO2, but not in pKSI, and the effect in wild-type cells was attenuated by calphostin C, confirming that it was mediated through PKC. This suggests that PKC may be involved in the phosphorylation and degradation of I-κBa, induced by PIF, necessary for the release of NF-κB from its inactive cytosolic complex.
AB - Proteolysis-inducing factor (PIF) is a sulphated glycoprotein produced by cachexia-inducing tumours, which initiates muscle protein degradation through an increased expression of the ubiquitin-proteasome proteolytic pathway. The role of kinase C (PKC) in PIF-induced proteasome expression has been studied in murine myotubes as a surrogate model of skeletal muscle. Proteasome expression induced by PIF was attenuated by 4α-phorbol 12-myristate 13-acetate (100 nM) and by the PKC inhibitors Ro31-8220 (10 μM), staurosporine (300 nM), calphostin C (300 nM) and Gö 6976 (200 μM). Proteolysis-inducing factor-induced activation of PKCα, with translocation from the cytosol to the membrane at the same concentration as that inducing proteasome expression, and this effect was attenuated by calphostin C. Myotubes transfected with a constitutively active PKCα (pCO2) showed increased expression of proteasome activity, and a longer time course, compared with their wild-type counterparts. In contrast, myotubes transfected with a dominant-negative PKCα (pKSI), which showed no activation of PKCα in response to PIF, exhibited no increase in proteasome activity at anytime point. Proteolysis-inducing factor-induced proteasome expression has been suggested to involve the transcription factor nuclear factor-κB (NF-κB), which may be activated through PKC. Proteolysis-inducing factor induced a decrease in cytosolic 1-κBα and an increase in nuclear binding of NF-κB in pCO2, but not in pKSI, and the effect in wild-type cells was attenuated by calphostin C, confirming that it was mediated through PKC. This suggests that PKC may be involved in the phosphorylation and degradation of I-κBa, induced by PIF, necessary for the release of NF-κB from its inactive cytosolic complex.
KW - Nuclear factor-κB
KW - Proteasome expression
KW - Protein kinase C
KW - Proteolysis-inducing factor
UR - http://www.scopus.com/inward/record.url?scp=2642526999&partnerID=8YFLogxK
UR - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2409757/
M3 - Article
C2 - 15150589
AN - SCOPUS:2642526999
SN - 0007-0920
VL - 90
SP - 1850
EP - 1857
JO - British Journal of Cancer
JF - British Journal of Cancer
IS - 9
ER -