TY - JOUR
T1 - Nuclear localization of a complex of fibroblast growth factor(FGF)-1 and an NH2-terminal fragment of FGF receptor isoforms R4 and R1 α in human liver cells
AU - Feng, Shuju
AU - Xu, Jianming
AU - Wang, Fen
AU - Kan, Mikio
AU - McKeehan, Wallace L.
N1 - Funding Information:
This work was supportedb y Public Health Service GrantsD K35310and DK38639 from the NationalI nstitute of Diabetesa nd Digestivea nd Kidney Diseasesa nd Grant CA59971 from the NationalC ancerInstitute.
PY - 1996/1/10
Y1 - 1996/1/10
N2 - FGF ligands and FGF receptor 1 (FGFR1) appear associated with the nucleus in addition to their extracellular and transmembrane locations. After receptor-dependent internalization in liver cells, radiolabeled 16-kDa FGF-1 appears in a 40-kDa covalent complex with a cellular protein. In this report, we show that in a human hepatoma cell line, HepG2, which expresses both FGFR4 and FGFR1, the 40-kDa complex cross-reacts with antibodies against the ectodomain of both types of receptors. In addition to antibody against FGF-1, a polyclonal antiserum against the three immunoglobulin (Ig)-like loop ectodomain of FGFR4 and a monoclonal antibody to a 19-residue sequence in the NH2-terminus of the NH2-terminal Ig Loop I of the three loop splice variant of FGFR1 (FGFR1α) reacts with the complex. A monoclonal antibody against an epitope in FGFR1 downstream of the inter-loop I/II sequence which reacts with intact FGFR1 failed to cross-react with the 40-kDa complex. Cell fractionations and indirect immunofluorescent localization revealed that the 40-kDa complex associates with the particulate fraction of cells, particularly the nucleus and associated cytoskeletal elements. We propose that the NH2-terminal Ig-loop of the three loop isoforms of FGFR, which are generally associated inversely with cell growth, may play a role at or in the nucleus in addition to modification of affinity of the FGFR ectodomain for heparan sulfate and FGF ligand.
AB - FGF ligands and FGF receptor 1 (FGFR1) appear associated with the nucleus in addition to their extracellular and transmembrane locations. After receptor-dependent internalization in liver cells, radiolabeled 16-kDa FGF-1 appears in a 40-kDa covalent complex with a cellular protein. In this report, we show that in a human hepatoma cell line, HepG2, which expresses both FGFR4 and FGFR1, the 40-kDa complex cross-reacts with antibodies against the ectodomain of both types of receptors. In addition to antibody against FGF-1, a polyclonal antiserum against the three immunoglobulin (Ig)-like loop ectodomain of FGFR4 and a monoclonal antibody to a 19-residue sequence in the NH2-terminus of the NH2-terminal Ig Loop I of the three loop splice variant of FGFR1 (FGFR1α) reacts with the complex. A monoclonal antibody against an epitope in FGFR1 downstream of the inter-loop I/II sequence which reacts with intact FGFR1 failed to cross-react with the 40-kDa complex. Cell fractionations and indirect immunofluorescent localization revealed that the 40-kDa complex associates with the particulate fraction of cells, particularly the nucleus and associated cytoskeletal elements. We propose that the NH2-terminal Ig-loop of the three loop isoforms of FGFR, which are generally associated inversely with cell growth, may play a role at or in the nucleus in addition to modification of affinity of the FGFR ectodomain for heparan sulfate and FGF ligand.
KW - Alternate splicing
KW - Monoclonal antibody
KW - Receptor metabolism
KW - Signal transduction
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U2 - 10.1016/0167-4889(95)00146-8
DO - 10.1016/0167-4889(95)00146-8
M3 - Article
C2 - 9244177
AN - SCOPUS:0030028359
SN - 0167-4889
VL - 1310
SP - 67
EP - 73
JO - Biochimica et Biophysica Acta - Molecular Cell Research
JF - Biochimica et Biophysica Acta - Molecular Cell Research
IS - 1
ER -