Molecular Cloning and Expression of Keratinocyte Proline-rich Protein, a Novel Squamous Epithelial Marker Isolated During Skin Development

Abstract

We describe a novel rat cDNA named keratinocyte proline-rich protein (KPRP) isolated by RNA differential display during skin development. We determine that KPRP is expressed in stratified squamous epithelium, and its ϳ2.8-kb cDNA encodes a 699-amino acid protein with high proline content (19%). KPRP is an insoluble protein, similar to most epidermal terminal differentiation-associated proteins. Immunoblot of the protein lysate from keratinocytes, using strong reducing conditions, demonstrates two KPRP bands of ϳ76 and 55 kDa size. KPRP is expressed in stratified squamous epithelia of skin, tongue, and esophagus. The initiation of KPRP expression in fetal rat skin at E17, E18, E19, E20, and E21 was analyzed by reverse transcription-PCR. Fetal skin at E19 and later expresses KPRP. In situ hybridization of skin from E18, E19, and 4-day-old neonatal rats demonstrates that interfollicular and follicular keratinocytes express KPRP. Anti-KPRP antibody demonstrates KPRP protein localizes to all layers of stratified epithelia in skin, tongue, and esophagus. In cultured dermal keratinocytes, KPRP is diffusely distributed throughout the cytoplasm with denser staining adjacent to the nuclear and plasma membranes. Additionally, immunoreactive intracellular granules are observed during keratinocyte detachment from their plastic substrate. Rat KPRP has 89% homology to a mouse genomic DNA sequence and 56% homology to a human hypothetical protein. We conclude that KPRP may be a new epidermal terminal differentiation-related protein expressed in stratified squamous epithelia. KPRP is expressed by fetal dermal keratinocytes during late gestation and is a new marker of maturing epidermis during fetal skin development.The epithelial layer of the skin provides an essential function as a protective barrier against insult from the outside environment. Although the adaptive barrier function of the epidermis begins during skin development, it is maintained after birth by the terminal differentiation process in the epidermis. Epidermal terminal differentiation genes have been well studied during the last decade, and at least 32 genes from three related families have been identified (1). The three terminal differentiation-related families are the cornified cell envelope (CE) 1 proteins, the keratin intermediate filament-associated proteins, and some calcium-binding proteins (2-5). These genes are clustered, have evolutionarily conserved structure, and are located on chromosome 1q21 in humans (6, 7) chromosome 3 in mice (8), and as we have determined for this study, chromosome 2 in rats. Additionally, the CE proteins have an ordered expression during fetal skin development. In humans, epidermal expression of involucrin begins at 14 weeks gestation when periderm is present. Loricrin and the small proline-rich proteins (SPRs) expression begins at 16 weeks when the epidermis is immature but already developing into a multilayered structure. Filaggrin and trichohyalin expression starts at 24 weeks, which is a developmental stage when the fetal s...

Transcriptome Profiles of Carcinoma-in-Situ and Invasive Non-Small Cell Lung Cancer as Revealed by SAGE

“…KRTDAP is associated with epidermal morphogenesis, and is a potential regulator of keratinocyte differentiation [70], [71], [72], [73], [74]. KPRP is an epidermal marker expressed in stratified squamous epithelia [75], and has a potential role in calcium-induced keratinocyte differentiation, and expression is increased in psoriasis [76]. It is noted that genes associated with development of the cornified cell envelope encoded on 1q21/19q13, tend to be expressed at notably lower levels in invasive cancer relative to CIS (see Table S2 and Table S5).…”

Molecular Cloning and Expression of Human Keratinocyte Proline-Rich Protein (hKPRP), an Epidermal Marker Isolated from Calcium-Induced Differentiating Keratinocytes

“…In this study, we have cloned a novel keratinocytes differentiation related gene hKPRP by a PCR-based cDNA subtraction method. Based on the sequence analysis, hKPRP is though to be a homolog of rat KPRP isolated by Kong et al (2003). The full-length cDNA of hKPRP is about 2.5 kb and predicted to encode 579 amino acid protein with a calculated molecular mass of 64 kDa and an isoelectric point (IP) of 8.72, which is little different from rat KPRP with 699 amino acids, 76.4 kDa molecular mass and 8.4 IP.…”

“…These include transglutaminase 1 and 3 (TGase 1 and 3), involucrin, cornifin, loricrin, filaggrin, and small proline-rich proteins (SPR) (Rice and Green, 1977;Fuchs, 1993;Steinert and Marekov, 1995;Steinert and Marekov, 1997;Nemes and Steinert, 1999). Interestingly, many of these genes have evolutionarily conserved structure, and are clustered on chromosome 1q21 in humans (Volz et al, 1993), chromosome 3 in mice , and chromosome 2 in rats (Kong et al, 2003). Despite intensive investigation during the last decades, however, many genes related to keratinocytes differentiation remain to be discovered.…”

Human alpha and beta papillomaviruses use different synonymous codon profiles

“…We postulate that these differences could be related to the tissue-specific differences of the two genera. Recent work on keratinocyte proline-rich protein (KPRP) in several laboratories [36, 37] discusses the association of this protein with the cornified envelope in terminally differentiating keratinocytes. We wonder if the beta virus E4 proteins, which are especially proline rich, might subvert this association with an interaction of their own to foster the ultimate release of the virus.…”