Identification of p62, a phosphotyrosine independent ligand of p56lck kinase, as a major component of intracytoplasmic hyaline bodies in hepatocellular carcinoma.
Intracytoplasmic hyaline bodies (IHBs) resemble a peculiar type of cytoplasmic inclusions in cells of hepatocellular carcinoma (HCC) which so far have escaped further characterization. In order to determine protein composition of IHBs we investigated tissue of a HCC containing numerous IHBs by immunohistochemistry and Western blot analysis using a large panel of different antibodies. 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) and on proteins hyperphosphorylated by mitotic kinases (MPM-2), respectively. In two-dimensional Western blots of HCC extracts SMI 31 and MPM-2 antibodies detected a 62 to 65 kD protein with an isoelectric point around 4.5. Microsequencing identified this protein as p62, a recently identified phosphotyrosine-independent ligand of the SH2 domain of tyrosine kinase p56lck. Immunoreactivity of p62 protein spots with antibodies to phosphorylated epitopes (i.e. SMI 31 and MPM-2) suggest that p62 is highly phosphorylated in IHBs. This is the first report on accumulation of p62 as cellular inclusions and its association with human disease.
Stumptner
C
C
Department of Pathology, University of Graz, Austria.
Heid
H
H
Zatloukal
K
K
Fuchsbichler
A
A
Hauser
H
H
Denk
H
H
D048868:Adaptor Proteins, Signal Transducing / Q000032:analysis* / Q000737:chemistry; D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm / Q000032:analysis; D006528:Carcinoma, Hepatocellular / Q000201:enzymology / Q000473:pathology*; D003593:Cytoplasm / Q000473:pathology; D006801:Humans; D002479:Inclusion Bodies / Q000201:enzymology / Q000473:pathology*; D008113:Liver Neoplasms / Q000201:enzymology / Q000473:pathology*; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000378:metabolism*; D008969:Molecular Sequence Data; D019000:Phosphotyrosine / Q000378:metabolism; D000071456:Sequestosome-1 Protein
D048868:Adaptor Proteins, Signal Transducing; D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; C099718:SQSTM1 protein, human; D000071456:Sequestosome-1 Protein; D019000:Phosphotyrosine; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck)