RESUMO
We have identified a novel protein, Leprecan-like 1 (LEPREL1), with profound similarity to the Leprecan family of proteoglycans. The genomic organization of the Leprecan gene family was found to be highly conserved. Expression analysis shows that LEPREL1 is expressed in most tissues as a 3.4 kb transcript encoding an 80 kDa protein. A LEPREL1 specific antibody stains many cell types including adipocytes and neuroendocrine cells of the gastrointestinal epithelium. Muscle tissue contains a specific 6.5 kb transcript and a 200 kDa protein. The 3.4 kb LEPREL1 transcript encodes a 708 amino acid protein containing a signal sequence, four tetratricopeptide repeats (TPRs), a leucine zipper, a P-loop, a prolyl 4-hydroxylase alpha domain (P4Halpha), and a C-terminal KDEL ER-retention motif. LEPREL1 is localized to the ER and Golgi network and over-expressing it affects normal protein disulfide isomerase staining patterns in the ER.
Assuntos
Retículo Endoplasmático/metabolismo , Fibrossarcoma/metabolismo , Complexo de Golgi/metabolismo , Glicoproteínas de Membrana/química , Glicoproteínas de Membrana/metabolismo , Proteoglicanas/química , Proteoglicanas/metabolismo , Análise de Sequência de Proteína , Homologia de Sequência de Aminoácidos , Sequência de Aminoácidos , Animais , Linhagem Celular Tumoral , Retículo Endoplasmático/ultraestrutura , Fibrossarcoma/genética , Complexo de Golgi/ultraestrutura , Humanos , Glicoproteínas de Membrana/genética , Camundongos , Dados de Sequência Molecular , Especificidade de Órgãos , Prolil Hidroxilases , Proteoglicanas/genética , Especificidade da Espécie , Distribuição TecidualRESUMO
Smad3 is one of the signal transducers that are activated in response to transforming growth factor-beta (TGF-beta). We have identified and characterized a splicing variant of smad3. The splicing variant (smad3-Delta3) lacks exon 3 resulting in a truncated linker region. We could detect mRNA expression of smad3-Delta3 in all investigated human tissues. Real-time PCR analyses demonstrated that the fraction of smad3-Delta3 mRNA compared to normal smad3 varies between tissues. The amount of spliced mRNA was estimated to represent 0.5-5% of the normal smad3 mRNA. When smad3-Delta3 is overexpressed in a fibrosarcoma cell line, the Smad3-Delta3 is translocated to the nucleus upon TGF-beta stimulation and binds the Smad responsive element. Using a CAGA luciferase reporter system, we demonstrate that Smad3-Delta3 has transcriptional activity and we conclude that Smad3-Delta3 possesses functional transactivating properties.
