title: SPINK5, the defective gene in netherton syndrome, encodes multiple LEKTI isoforms derived from alternative pre-mRNA processing.
abstract: The multidomain serine protease inhibitor lymphoepithelial Kazal-type related inhibitor (LEKTI) represents a key regulator of the proteolytic events occurring during epidermal barrier formation and hair development, as attested by the severe autosomal recessive ichthyosiform skin condition Netherton syndrome (NS) caused by mutations in its encoding gene, serine protease inhibitor Kazal-type 5 (SPINK5). Synthesized as a proprotein, LEKTI is rapidly cleaved intracellularly, thus generating a number of potentially bioactive fragments that are secreted. Here, we show that SPINK5 generates three classes of transcripts encoding three different LEKTI isoforms, which differ in their C-terminal portion. In addition to the previously described 15 domain isoform, SPINK5 encodes a shorter LEKTI isoform composed of only the first 13 domains, as well as a longer isoform carrying a 30-amino-acid residue insertion between the 13th and 14th inhibitory domains. We demonstrate that variable amounts of SPINK5 alternative transcripts are detected in all SPINK5 transcriptionally active tissues. Finally, we show that in differentiated cultured human keratinocytes all SPINK5 alternative transcripts are translated into protein and that the LEKTI precursors generate distinct secreted C-terminal proteolytic fragments from a similar cleavage site. Since several data indicate a biological role for the pro-LEKTI-cleaved polypeptides, we hypothesize that the alternative processing of the SPINK5 pre-messenger RNA represents an additional mechanism to further increase the structural and functional diversity of the LEKTI bioactive fragments.
authors.affiliation: Laboratory of Molecular and Cell Biology, Istituto Dermopatico dell'Immacolata, IDI-IRCCS, Rome, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Tartaglia-Polcini
authors.forename: Chrystelle
authors.initials: C
authors.lastname: Bonnart
authors.forename: Alessia
authors.initials: A
authors.lastname: Micheloni
authors.forename: Francesca
authors.initials: F
authors.lastname: Cianfarani
authors.forename: Alessandra
authors.initials: A
authors.lastname: Andrè
authors.forename: Giovanna
authors.initials: G
authors.lastname: Zambruno
authors.forename: Alain
authors.initials: A
authors.lastname: Hovnanian
authors.forename: Marina
authors.initials: M
authors.lastname: D'Alessio
mesh_terms: D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000235:genetics*; D002454:Cell Differentiation; D002478:Cells, Cultured; D006801:Humans; D007057:Ichthyosis / Q000235:genetics*; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis / Q000235:genetics; D020033:Protein Isoforms / Q000235:genetics; D053491:Proteinase Inhibitory Proteins, Secretory; D012322:RNA Precursors / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D000074163:Serine Peptidase Inhibitor Kazal-Type 5; D013577:Syndrome; D014158:Transcription, Genetic
chemical_list: D002352:Carrier Proteins; D020033:Protein Isoforms; D053491:Proteinase Inhibitory Proteins, Secretory; D012322:RNA Precursors; D012333:RNA, Messenger; C120650:SPINK5 protein, human; D000074163:Serine Peptidase Inhibitor Kazal-Type 5