Analysis of intracytoplasmic hyaline bodies in a hepatocellular carcinoma. Demonstration of p62 as major constituent.
Intracytoplasmic hyaline bodies (IHBs) resemble inclusions in hepatocellular carcinoma cells, which so far have escaped further characterization. A relationship to Mallory bodies was suggested on the basis of light microscopy and filamentous ultrastructure. A hepatocellular carcinoma containing numerous IHBs was studied. Our studies revealed immunoreactivity of IHBs with the monoclonal antibodies SMI 31 and MPM-2, which recognize hyperphosphorylated epitopes present on paired helical filaments in Alzheimer's disease brains (SMI 31) or on diverse proteins hyperphosphorylated by mitotic kinases in the M-phase of the cell cycle (MPM-2). One- and two-dimensional gel electrophoresis of tumor extracts followed by immunoblotting with SMI 31 and MPM-2 antibodies revealed a major immunoreactive protein with an apparent molecular weight between 62 and 65 kd, which was resolved into several highly acidic (pH 4.5) protein components in two-dimensional gels. This protein was undetectable in non-neoplastic liver tissue. Sequence analysis identified the SMI 31 and MPM-2 immunoreactive material as p62, indicating that p62 is a major constituent of IHBs. p62 is an only recently discovered protein that is a phosphotyrosine-independent ligand of the SH2 domain of p56(lck), a member of the c-src family of cytoplasmic kinases. Moreover, p62 binds ubiquitin and may act as an adapter linking ubiquitinated species to other proteins. These features suggest a role of p62 in signal transduction and possibly also carcinogenesis. IHBs observed in the hepatocellular carcinoma cells presented are the first indications of a role of p62 in disease.
Stumptner
C
C
Departments of Pathology* and Surgery,double dagger University of Graz School of Medicine, Graz, Austria.
Heid
H
H
Fuchsbichler
A
A
Hauser
H
H
Mischinger
H J
HJ
Zatloukal
K
K
Denk
H
H
D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000378:metabolism* / Q000473:pathology / Q000648:ultrastructure; D002352:Carrier Proteins / Q000276:immunology / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D017809:Fatal Outcome; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D006818:Hyalin / Q000378:metabolism* / Q000648:ultrastructure; D017874:Immediate-Early Proteins / Q000276:immunology / Q000378:metabolism*; D007150:Immunohistochemistry; D002479:Inclusion Bodies / Q000378:metabolism* / Q000648:ultrastructure; D008113:Liver Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000648:ultrastructure; D008297:Male; D008854:Microscopy, Electron; D008875:Middle Aged; D008969:Molecular Sequence Data; D011506:Proteins; D017421:Sequence Analysis; D000071456:Sequestosome-1 Protein
D048868:Adaptor Proteins, Signal Transducing; D000911:Antibodies, Monoclonal; D002352:Carrier Proteins; D017874:Immediate-Early Proteins; D011506:Proteins; C099718:SQSTM1 protein, human; D000071456:Sequestosome-1 Protein