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Gene Review

KRT32  -  keratin 32, type I

Homo sapiens

Synonyms: HA2, HHA2, HKA2, Ha-2, Hair keratin, type I Ha2, ...
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Disease relevance of KRT32

  • At calcium-specific ionophore A23187 concentrations of approximately 0.25 microM [which still allow assembly and release of fowl plague virus (FPV) particles] post-translational proteolytic cleavage of the viral hemagglutinin precursor HA into the fragments HA1 and HA2 is inhibited [1].
  • The results clearly show that residues 1-11 of HA2 represent an important antigenic site on influenza virus [2].
  • These results suggest that protonation of the NH2-terminal segment of the HA2 form causes interaction of the segment with the lipid core of the target cell membrane, leading to hemolysis and fusion [3].
  • This finding implies that in vitro generated HA-1- and HA-2-specific cytotoxic T lymphocytes could be used as adoptive immunotherapy to treat hematological malignancies relapsing after alloSCT [4].
  • The ex vivo-generated HA-1- and HA-2-specific CTLs efficiently lyse leukemic cells derived from acute myeloid leukemia (AML) and acute lymphoid leukemia (ALL) patients [5].

High impact information on KRT32

  • The mutants included proline substitutions at HA2 55, 71, and 80, as well as a double proline substitution at residues 55 and 71 [6].
  • Here we examine the structure of TBHA2 with the electron microscope and compare it with the fusion pH structure of HA2 in virosomes, HA2 in aggregates formed at fusion pH by the soluble, bromelain-released ectodomain BHA and HA2 in liposomes with which BHA associates at fusion pH [7].
  • In contrast, immunofluorescence microscopy using antibodies specific for the alpha- and beta-adaptins, respectively, and immunogold labeling of cryosections with anti-alpha-adaptin antibodies shows that under these conditions HA2 adaptors are aggregated at the plasma membrane to the same extent as in control cells [8].
  • Acidification of the cytosol affects neither clathrin nor HA2 adaptors as studied by immunofluorescence microscopy [8].
  • The effects of methods known to perturb endocytosis from clathrin-coated pits on the localization of clathrin and HA2 adaptors in HEp-2 carcinoma cells have been studied by immunofluorescence and ultrastructural immunogold microscopy, using internalization of transferrin as a functional assay [8].

Chemical compound and disease context of KRT32

  • The influenza virus hemagglutinin polypeptides, HA1 and HA2, have been purified by gel filtration in the presence of sodium dodecyl sulfate from a vaccine preparation of the recombinant strain Heq1N2 [9].
  • To overcome this problem, in the present study, polyarginine-fused p53 was linked with the NH(2)-terminal domain of influenza virus hemagglutinin-2 subunit (HA2), which is a pH-dependent fusogenic peptide that induces the lysis of membranes at low pH levels [10].
  • Proteolytic cleavage of influenza virus hemagglutinin (HA) glycoprotein into subunits designated HA1 and HA2 is required for penetration of virus into the cell [11].
  • The haemagglutinin from the Hong Kong influenza virus A/Memphis/102/72 contains seven oligosaccharide units attached to asparagine residues 8, 22, 38, 81, 165 and 285 in the heavy chain (HA1) and to residue 154 in the light chain (HA2) [12].
  • These mutations comprised a single Glu replacement for Gly at the N-terminus ("El" mutant) or at position 4 ("E4") of the HA2 subunit and were shown to produce striking alterations in virus-induced hemolysis and syncytia formation, especially for E1 [13].

Biological context of KRT32

  • DAPI banding of the chromosomes allowed sublocalization of the hHa2 gene to 17q12-q21 and the hHb1 gene to 12q13, i.e., gene loci that have also been previously determined for human type I and type II epithelial keratins [14].
  • The specific 3'-noncoding sequences of hHa2 and hHb1 were also used to isolate genomic fragments for both keratins from human genomic libraries which were than used for fluorescence in situ hybridization to human metaphase chromosomes [14].
  • To induce membrane fusion, we used (i) influenza hemagglutinin peptide (HA), a 20-aa peptide derived from the N-terminal fusion peptide region of the HA2 subunit, and (ii) two synthetic analogue peptides of HA, a negatively (E5) and positively (K5) charged analogue [15].
  • Hematopoiesis-restricted minor histocompatibility antigens HA-1- or HA-2-specific T cells can induce complete remissions of relapsed leukemia [4].
  • The attachment to liposomes exhibited the same pH dependence and rapid kinetics as the conformational change and was mediated by HA2 [16].

Anatomical context of KRT32

  • Clathrin and HA2 adaptors: effects of potassium depletion, hypertonic medium, and cytosol acidification [8].
  • We propose that the hydrophobic NH2-terminal segment of HA2 is exposed during the structural change and interacts with the target membranes, causing a permeability increase and leading to hemolysis and lysis [17].
  • Thus, HA-1- and HA-2-specific cytotoxic T lymphocytes emerging in the blood of patients after DLI demonstrate graft-versus-leukemia or myeloma reactivity resulting in a durable remission [4].
  • One of the transfectants specifically reacts with one alloantiserum (HA2) that detects HLA class I molecules specific to HLA-A2-positive, phytohemagglutinin-activated T cells and not found on resting T or B cells [18].
  • Furthermore, cloned tetramer-positive T cells isolated during the clinical response specifically recognized HA-1 and HA-2 expressing malignant progenitor cells of the recipient and inhibited the growth of leukemic precursor cells in vitro [4].

Associations of KRT32 with chemical compounds

  • These include a hydrophobic signal peptide, hydrophobic NH2 and COOH termini of the HA2 subunit, and a HA1/HA2 cleavage site involving an arginine residue [19].
  • The composition of the 50 residue peptide associated with the membrane, which is removed from the C-terminus of HA2 by bromelain, is deduced and shown to be hydrophobic and contain 50% of the serine residues of HA2 [20].
  • (1) as the intact hemagglutinin after disruption of the virus in sodium dodecyl sulfate, giving 2 subunits of 58,000 daltons (HA1) and 26,000 daltons (HA2), and (2) after treatment of the virus with bromelain, giving 2 subunits of 58,000 daltons (BHA1) and 21,000 daltons (BHA2) [20].
  • These results suggest that protein transduction therapy using polyarginine and HA2 may be useful as a method for cancer therapy [10].
  • These enzymes, designated PTPases HA1 and HA2, were purified approximately 20,000-fold and approximately 15,000-fold, respectively, and shown to differ markedly in their sensitivity to both vanadate and phosphotyrosine [21].

Analytical, diagnostic and therapeutic context of KRT32

  • Amino-terminal sequence analysis of the smaller polypeptide, HA2, revealed a cyclic repetition of glycyl residues through the first 24 residues at every third to fourth position [9].
  • The fusion activity of influenza hemagglutinin (HA) and of HA proteins altered in the amino terminus of HA2 (fusion peptide) by site-directed mutagenesis (Gething, M.-J., Doms, R. W., York, D., and White, J. (1986) J. Cell Biol. 102, 11-23) was analyzed following expression in CV-1 cells using SV40-HA recombinant virus vectors [22].
  • Pulse-chase labeling with [(35)S]methionine and Western blot analysis with anti-HA antibodies of cellular and virion polypeptides showed that HAEC cleaved newly synthesized HA0 to HA1/HA2 ("cleavage from within") and significant amounts of cleaved HA accumulated within cells [23].
  • Fraction 18 of the high-performance liquid chromatography (HPLC)-separated HLA-A2.1 peptide pool was found to contain the natural HA-2 peptide [24].
  • Purified HLA-A2.1 molecules obtained by affinity chromatography of 6 x 10(10) Epstein Barr virus (EBV)-transformed B lymphocytes were used in an attempt to isolate the human HLA-A2.1-restricted minor histocompatibility (H) peptides H-Y and HA-2 [24].


  1. Inhibition of proteolytic cleavage of the hemagglutinin of influenza virus by the calcium-specific ionophore A23187. Klenk, H.D., Garten, W., Rott, R. EMBO J. (1984) [Pubmed]
  2. Localization, synthesis, and activity of an antigenic site on influenza virus hemagglutinin. Atassi, M.Z., Webster, R.G. Proc. Natl. Acad. Sci. U.S.A. (1983) [Pubmed]
  3. Interaction of influenza virus hemagglutinin with target membrane lipids is a key step in virus-induced hemolysis and fusion at pH 5.2. Maeda, T., Kawasaki, K., Ohnishi, S. Proc. Natl. Acad. Sci. U.S.A. (1981) [Pubmed]
  4. Hematopoiesis-restricted minor histocompatibility antigens HA-1- or HA-2-specific T cells can induce complete remissions of relapsed leukemia. Marijt, W.A., Heemskerk, M.H., Kloosterboer, F.M., Goulmy, E., Kester, M.G., van der Hoorn, M.A., van Luxemburg-Heys, S.A., Hoogeboom, M., Mutis, T., Drijfhout, J.W., van Rood, J.J., Willemze, R., Falkenburg, J.H. Proc. Natl. Acad. Sci. U.S.A. (2003) [Pubmed]
  5. Feasibility of immunotherapy of relapsed leukemia with ex vivo-generated cytotoxic T lymphocytes specific for hematopoietic system-restricted minor histocompatibility antigens. Mutis, T., Verdijk, R., Schrama, E., Esendam, B., Brand, A., Goulmy, E. Blood (1999) [Pubmed]
  6. Specific single or double proline substitutions in the "spring-loaded" coiled-coil region of the influenza hemagglutinin impair or abolish membrane fusion activity. Qiao, H., Pelletier, S.L., Hoffman, L., Hacker, J., Armstrong, R.T., White, J.M. J. Cell Biol. (1998) [Pubmed]
  7. Electron microscopy of antibody complexes of influenza virus haemagglutinin in the fusion pH conformation. Wharton, S.A., Calder, L.J., Ruigrok, R.W., Skehel, J.J., Steinhauer, D.A., Wiley, D.C. EMBO J. (1995) [Pubmed]
  8. Clathrin and HA2 adaptors: effects of potassium depletion, hypertonic medium, and cytosol acidification. Hansen, S.H., Sandvig, K., van Deurs, B. J. Cell Biol. (1993) [Pubmed]
  9. Chromatographic isolation of the hemagglutinin polypeptides from influenza virus vaccine and determination of their amino-terminal sequences. Bucher, D.J., Li, S.S., Kehoe, J.M., Kilbourne, E.D. Proc. Natl. Acad. Sci. U.S.A. (1976) [Pubmed]
  10. The NH2 terminus of influenza virus hemagglutinin-2 subunit peptides enhances the antitumor potency of polyarginine-mediated p53 protein transduction. Michiue, H., Tomizawa, K., Wei, F.Y., Matsushita, M., Lu, Y.F., Ichikawa, T., Tamiya, T., Date, I., Matsui, H. J. Biol. Chem. (2005) [Pubmed]
  11. Role of respiratory tract proteases in infectivity of influenza A virus. Barbey-Morel, C.L., Oeltmann, T.N., Edwards, K.M., Wright, P.F. J. Infect. Dis. (1987) [Pubmed]
  12. Carbohydrate composition of the oligosaccharide units of the haemagglutinin from the Hong Kong influenza virus A/Memphis/102/72. Ward, C.W., Gleeson, P.A., Dopheide, T.A. Biochem. J. (1980) [Pubmed]
  13. Membrane fusion activity of the influenza virus hemagglutinin: interaction of HA2 N-terminal peptides with phospholipid vesicles. Rafalski, M., Ortiz, A., Rockwell, A., van Ginkel, L.C., Lear, J.D., DeGrado, W.F., Wilschut, J. Biochemistry (1991) [Pubmed]
  14. Sequence data and chromosomal localization of human type I and type II hair keratin genes. Rogers, M.A., Nischt, R., Korge, B., Krieg, T., Fink, T.M., Lichter, P., Winter, H., Schweizer, J. Exp. Cell Res. (1995) [Pubmed]
  15. Microscopic observations reveal that fusogenic peptides induce liposome shrinkage prior to membrane fusion. Nomura, F., Inaba, T., Ishikawa, S., Nagata, M., Takahashi, S., Hotani, H., Takiguchi, K. Proc. Natl. Acad. Sci. U.S.A. (2004) [Pubmed]
  16. Membrane fusion activity of the influenza virus hemagglutinin. The low pH-induced conformational change. Doms, R.W., Helenius, A., White, J. J. Biol. Chem. (1985) [Pubmed]
  17. Hemolytic activity of influenza virus hemagglutinin glycoproteins activated in mildly acidic environments. Sato, S.B., Kawasaki, K., Ohnishi, S. Proc. Natl. Acad. Sci. U.S.A. (1983) [Pubmed]
  18. Isolation of a human major histocompatibility complex class I gene encoding a nonubiquitous molecule expressed on activated lymphocytes. Paul, P., Fauchet, R., Boscher, M.Y., Sayagh, B., Masset, M., Medrignac, G., Dausset, J., Cohen, D. Proc. Natl. Acad. Sci. U.S.A. (1987) [Pubmed]
  19. Evolution of influenza A and B viruses: conservation of structural features in the hemagglutinin genes. Krystal, M., Elliott, R.M., Benz, E.W., Young, J.F., Palese, P. Proc. Natl. Acad. Sci. U.S.A. (1982) [Pubmed]
  20. Studies on the primary structure of the influenza virus hemagglutinin. Skehel, J.J., Waterfield, M.D. Proc. Natl. Acad. Sci. U.S.A. (1975) [Pubmed]
  21. Phosphotyrosyl turnover in insulin signaling. Characterization of two membrane-bound pp15 protein tyrosine phosphatases from 3T3-L1 adipocytes. Liao, K., Hoffman, R.D., Lane, M.D. J. Biol. Chem. (1991) [Pubmed]
  22. Role of the fusion peptide sequence in initial stages of influenza hemagglutinin-induced cell fusion. Schoch, C., Blumenthal, R. J. Biol. Chem. (1993) [Pubmed]
  23. Cleavage of influenza a virus hemagglutinin in human respiratory epithelium is cell associated and sensitive to exogenous antiproteases. Zhirnov, O.P., Ikizler, M.R., Wright, P.F. J. Virol. (2002) [Pubmed]
  24. Isolation of an HLA-A2.1 extracted human minor histocompatibility peptide. de Bueger, M., Verreck, F., Blokland, E., Drijfhout, J.W., Amons, R., Koning, F., Goulmy, E. Eur. J. Immunol. (1993) [Pubmed]
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