Characterization of the proteins of guinea-pig hair and hair-follicle tissue

The keratins of the human beard hair medulla: the riddle in the middle

We have investigated the expression of 52 of the 54 keratins in beard hair medulla. We found that not only 12 hair keratins but, unexpectedly, also 12 epithelial keratins are potentially expressed in medulla cells. The latter comprise keratins also present in outer- and inner-root sheaths and in the companion layer. Keratins K5, K14, K17, K25, K27, K28, and K75 define a "pre-medulla," composed of cells apposed to the upper dermal papilla. Besides K6, K16, K7, K19, and K80, all pre-medullary epithelial keratins continue to be expressed in the medulla proper, along with the 12 hair keratins. Besides this unique feature of cellular keratin co-expression, the keratin pattern itself is highly variable in individual medulla cells. Remarkably, both epithelial and hair keratins behave highly promiscuously with regard to heterodimer- and IF formation, which also includes keratin chain interactions in IF bundles. We also identified cortex cells within the medullary column. These exhibit all the properties of genuine cortex cells, including a particular type of keratin heterogeneity of their compact IF bundles. In both keratin expression profile and keratin number, medulla cells are distinct from all other cells of the hair follicle or from any other epithelium.

Colorimetric determination of citrulline residues in proteins

A method is described for the direct colorimetric determination of citrulline residues in proteins based on the reaction with diacetylmonoxime in the presence of lower concentrations of sulfuric acid. The reduced sensitivity due to the lower acid concentration was overcome by the addition of ferric chloride which also contributed to the color stabilization. Insoluble proteins or proteins resulting in turbidity can be analyzed following partial hydrolysis of those with enzyme or acid. The molar absorption coefficient (epsilon) for citrulline at 464 nm was 2.8 x 10(4). The method enabled us to determine low levels of protein-bound citrulline which are beyond the limitations of conventional methods using an amino acid analyzer. We determined the citrulline contents in the cornified cells of the epidermis of newborn rats, as well as soybean trypsin inhibitor.

Normalization of hair growth in sparse fur-abnormal skin and hair (SPF-ASH) mice by introduction of the rat ornithine transcarbamylase (OTC) gene

The sparse fur-abnormal skin and hair (SPF-ASH) mouse is a model for the human X-linked hereditary disease, ornithine transcarbamylase (OTC) deficiency. This condition is characterized by abnormal skin and delayed hair growth, hyperammonemia, orotic aciduria and low levels of serum citrulline and arginine. Murakami et al. [1] established a line of transgenic mice, by introducing the recombinant rat OTC (rOTC) gene into fertilized C57BL mouse eggs. We introduced the rOTC gene into SPF-ASH mice by mating SPF-ASH heterozygotes and transgenic mice, which carried this gene. The hemizygous SPF-ASH mice bearing the rOTC gene showed normal hair growth without sparse fur, normal urinary orotic acid excretion and normal serum citrulline and arginine levels. These mice showed OTC activities 2 and 6 times higher in the liver and small intestine, respectively, than the SPF-ASH mice but about 12% and 27% those of the controls [2].

Structure and biochemistry of mammalian hard keratin

In this review, the structure and biological formation of hard alpha-keratin are drawn together. The hard keratins comprising wool, hairs, quills, hooves, horns, nails and baleen contain partly alpha-helical polypeptides which show homology with epidermal polypeptides only in the helical regions. These polypeptides (about 32 chains) are organized into intermediate filaments (IFs) of 7.5 nm diameter which are embedded in variable amounts of a matrix of non-helical cystine-rich proteins and glycine-tyrosine-rich proteins. The total number of proteins may exceed 100. In addition keratins contain a variety of lipid components. Wool and hair are produced in follicles in a multistep procedure. In the lower levels of the follicle, IFs without associated matrix are found. Subsequently matrix proteins are laid down between the IFs and further synthesis takes place concurrently. Finally the proteins are insolubilized by the oxidative formation of disulphide bonds. Keratinized fibres shows considerable complexity and diversity in the structural arrangement of IFs and matrix within cortical cells. Typically the IFs show hexagonal packing or give a whorl-like appearance in cross-section.

Amino acid compositions of human hair fibrous protein components purified with two-dimensional electrophoresis

Normal human S-carboxymethylated (SCM) hair fibrous protein (HFP) components were purified with two-dimensional electrophoresis, and their amino acid compositions were examined. As previously reported, the SCM cysteine and glycine contents of the crude HFPs were characteristically high and low, respectively, as compared with those reported for the stratum corneum fibrous proteins (SCFPs). However, the SCM cysteine and glycine contents of the purified SCM HFP components were not as high or as low, respectively, but were rather very similar to those of the SCFPs. This suggests that, with respect to cysteine and glycine content, fibrous protein components similar to those of the stratum corneum exist in normal human hair.

Expression of keratin K14 in the epidermis and hair follicle: insights into complex programs of differentiation

Keratins K14 and K5 have long been considered to be biochemical markers of the stratified squamous epithelia, including epidermis (Moll, R., W. Franke, D. Schiller, B. Geiger, and R. Krepler. 1982. Cell. 31:11-24; Nelson, W., and T.-T. Sun. 1983. J. Cell Biol. 97:244-251). When cells of most stratified squamous epithelia differentiate, they downregulate expression of mRNAs encoding these two keratins and induce expression of new sets of keratins specific for individual programs of epithelial differentiation. Frequently, as in the case of epidermis, the expression of differentiation-specific keratins also leads to a reorganization of the keratin filament network, including denser bundling of the keratin fibers. We report here the use of monospecific antisera and cRNA probes to examine the differential expression of keratin K14 in the complex tissue of human skin. Using in situ hybridizations and immunoelectron microscopy, we find that the patterns of K14 expression and filament organization in the hair follicle are strikingly different from epidermis. Some of the mitotically active outer root sheath (ORS) cells, which give rise to ORS under normal circumstances and to epidermis during wound healing, produce only low levels of K14. These cells have fewer keratin filaments than basal epidermal cells, and the filaments are organized into looser, more delicate bundles than is typical for epidermis. As these cells differentiate, they elevate their expression of K14 and produce denser bundles of keratin filaments more typical of epidermis. In contrast to basal cells of epidermis and ORS, matrix cells, which are relatively undifferentiated and which can give rise to inner root sheath, cuticle and hair shaft, show no evidence of K14, K14 mRNA expression, or keratin filament formation. As matrix cells differentiate, they produce hair-specific keratins and dense bundles of keratin filaments but they do not induce K14 expression. Collectively, the patterns of K14 and K14 mRNA expression and filament organization in mitotically active epithelial cells of the skin correlate with their relative degree of pluripotency, and this suggests a possible basis for the deviation of hair follicle programs of differentiation from those of other stratified squamous epithelia.

Cultivation of murine hair follicles as organoids in a collagen matrix

Techniques are described for the isolation and cultivation of functionally intact mouse hair follicles. Follicles were isolated by collagenase digestion of dermis from 5-day-old mice and purified by differential centrifugation and filtration. Purified follicles were cultured in a Type 1 collagen matrix using Medium 199 and 8% fetal calf serum as the basic nutrient. Viability of follicles was maintained in culture since the cultures incorporated thymidine into DNA and methionine into proteins for at least 7 days. Furthermore, follicles isolated from the collagen matrix after 7 days could reattach to a plastic culture substrate or be further cultivated in a fresh collagen matrix. Functional integrity of cultured follicles was maintained since some follicle-specific cytoskeletal proteins were synthesized in vitro, and follicles isolated from the collagen matrix after 7 days formed a haired skin when recombined with dermal fibroblasts and grafted to a skin site on nude mice. Only a minority of follicles appeared to produce a mature hair shaft in vitro by morphologic criteria, however, and synthesis of the total complement of hair proteins was not observed. Cholera toxin was a strong mitogen for cultured follicles, whereas epidermal growth factor was slightly mitogenic. Epidermal growth factor stimulated the release of a Type 1 collagenase by follicle cells, however. This model system provides an opportunity for the systematic analysis of factors required for the induction of hair growth and the underlying physiology of hair follicle development. This model should also be useful for studying the role of the hair follicle in skin carcinogenesis.

Acidic and basic hair/nail ("hard") keratins: their colocalization in upper cortical and cuticle cells of the human hair follicle and their relationship to "soft" keratins

Although numerous hair proteins have been studied biochemically and many have been sequenced, relatively little is known about their in situ distribution and differential expression in the hair follicle. To study this problem, we have prepared several mouse monoclonal antibodies that recognize different classes of human hair proteins. Our AE14 antibody recognizes a group of 10-25K hair proteins which most likely corresponds to the high sulfur proteins, our AE12 and AE13 antibodies define a doublet of 44K/46K proteins which are relatively acidic and correspond to the type I low sulfur keratins, and our previously described AE3 antibody recognizes a triplet of 56K/59K/60K proteins which are relatively basic and correspond to the type II low sulfur keratins. Using these and other immunological probes, we demonstrate the following. The acidic 44K/46K and basic 56-60K hair keratins appear coordinately in upper corticle and cuticle cells. The 10-25K, AE14-reactive antigens are expressed only later in more matured corticle cells that are in the upper elongation zone, but these antigens are absent from cuticle cells. The 10-nm filaments of the inner root sheath cells fail to react with any of our monoclonal antibodies and are therefore immunologically distinguishable from the cortex and cuticle filaments. Nail plate contains 10-20% soft keratins in addition to large amounts of hair keratins; these soft keratins have been identified as the 50K/58K and 48K/56K keratin pairs. Taken together, these results suggest that the precursor cells of hair cortex and nail plate share a major pathway of epithelial differentiation, and that the acidic 44K/46K and basic 56-60K hard keratins represent a co-expressed keratin pair which can serve as a marker for hair/nail-type epithelial differentiation.

The presence of citrulline in epidermal proteins

Citrulline is present in the stratum corneum proteins of human, cow snout, pig snout and guinea pig epidermis but is absent from the stratum corneum proteins of frog, mouse, turtle, rat and hamster epidermis. The amino acid is released by acid hydrolysis and ranges from 1.7 to 5.5 residues per thousand residues of protein amino acid. Protein derived citrulline co-chromatographs with authentic L-citrulline on an amino acid analyzer, on Dowex-50, on Dowex-2 and on thin-layer chromatography. Dansylated material co-chromatographed with authentic dansyl-L-citrulline in two thin-layer chromatography systems. Labelling experiments have shown that the protein bound citrulline is derived from protein bound arginine and probably results from enzymatic conversion of the guanido group to the ureido group.

The origin of citrulline-containing proteins in the hair follicle and the chemical nature of trichohyalin, an intracellular precursor

The present studies have demonstrated that the medulla and inner root sheath cells develop within their cytoplasm a protein that is unique in composition and is present in the trichohyalin granules. The protein is rich in arginine residues, some of which undergo a side-chain conversion in situ into citrulline residues. An unusual Ca2+-dependent enzyme activity distinguishable from cross-linking transamidase has been detected in the hair follicle and will act in vitro on trichohyalin protein as the natural substrate. The conversion in vivo must occur during the time that the medullary and inner root sheath cells move up the follicle and their cytoplasm fills with cross-linked protein containing citrulline. The function of citrulline in these proteins is not understood but its formation is a major process during hair growth.

Immunochemical studies on blood group A substance from human hair

Blood group A-active substance was extracted from urea-treated human hair uith methanol-ethyl ether 1:1, v/v) or chloroform-methanol (1:1, v/v). The serological activity of blood group A substance in the hair was destroyed by A-decomposing enzyme from Clostridium tertium with concomitant development of blood group H activity. It is concluded therefore that the extract from the hair of group A contained blood group A-active glycolipid with N-acetylgalactosamine as the non-reducing sugar.

A cystine-rich protein fraction from oxidized alpha-keratin

A soluble fraction of alpha-keratin was obtained on fission of disulphide bonds. The fraction was soluble in the oxidizing solution and would normally be lost when such procedures are used for isolating keratose fractions. This fraction, which constituted 6% by weight of keratin, was rich in cystine, and about 30% of the fraction had a mol.wt. of less than 20 000.

The polypeptide composition of bovine epidermal alpha-keratin

1. The polypedtide chains that comprise the subunits of the tonofilaments, or th alpha-keratin component, of bovine epidermis were fractionated by combination of chromatography on DEAE-cellulose and preparative polyacrylamide-gel electrophoresis. 2. The seve polypeptide chains investigated had generalyy similar properties; all contained two residues per molecule of tryptophan and N-acetylserine was the common N-terminal amino acid residue. 3. On the basis of close similarities in alpha-helix content and amino acid composition, the polypeptide chains were classified into three distinct groups. Each group contained approximately one-third of the total polypeptides on a molar basis. The groups and designated polypeptides chain numbers were: group one, polypeptides 1a and 1b, which had moleculae weights of 58,000, contained about 25% alpha-helix, 86 glutamic acid and 8 cysteine residues per molecule, but which differed in net charge, extinction coefficients and tyrosine contents; group two, polypeptides 2, 3, and 4, which hadmolecular weights within thewithin the range of 52,00-56,000, contained about 48% alpha-helix, 54 glutamic acid and 6 cysteine residues per molecule, but which differed in extinction coefficients and tryosine contents; and group, polypeptides 5 and 6, which had molecular weights of 47000-48000, contained about 56% alpha-helix, 64 glutamic acid and 4 cysteine residues per molecule, but which differed in extinction coefficients and tyrosine contents...

The extraction and characterization of bovine epidermal alpha-keratin

1. The alpha-fibrous protein (alpha-keratin) component of bovine epidermis has been extracted and characterized. 2. Prekeratin, a multichain unit of the epidermal tonofilaments, was shown to consist of six different polypeptide chains on polyacrylamide-gel systems containing sodium dodecyl sulphate or sodium decyl sulphate with discontinuous gel buffers, but only three chains were seen when a gel system containing sodium dodecyl sulphate with a continuous gel buffer was used. 3. Extraction of the 'keratinized' stratum corneum and the living part of the epidermis with urea buffers at pH 7.6 or 9.0 released 60% of the total dry weight of the tissues in the form of alpha-helical polypeptides. 4. The numbers, relative amounts and properties of the extracted polypeptides were the same as the subunits of prekeratin and thus are derived from the tonofilaments in situ. 5. The subunits of prekeratin and the polypeptides extracted from the living cell layers contained an average of six cysteine residues, but those from the stratum corneum contained an average of three intrachain disulphide bonds. 6. The polypeptide chains aggregated through non-covalent interactions in vitro into filaments that were similar to the tonofilaments. 7. Since the polypeptides could be released from the stratum corneum without breaking covalent bonds, it is concluded that such bonds do not cross-link the tonofilaments and non-fibrous keratohyalin. It is suggested that the tonofilaments and keratohyalin of bovine epidermis are associated by secondary bonding forces.