Biomedical subjects

R Maniwa

Publications and source records attributed to R Maniwa.

3 recordsLinked to original sources

PubMed2001

PAR-6 regulates aPKC activity in a novel way and mediates cell-cell contact-induced formation of the epithelial junctional complex.

BACKGROUND: PAR-6, aPKC and PAR-3 are polarity proteins that co-operate in the establishment of cell polarity in Caenorhabditis elegans and Drosophila embryos. We have recently shown that mammalian aPKC is required for the formation of the epithelia-specific cell-cell junctional structure. We have also revealed that a mammalian PAR-6 forms a ternary complex with aPKC and ASIP/PAR-3, and localizes at the most apical end of the junctional complex in epithelial cells. RESULTS: The ternary complex formation and junctional co-localization of PAR-6 with aPKC and ASIP/PAR-3 are observed during the early stage of epithelial cell polarization. In addition, over-expression of the PAR-6 mutant with CRIB/PDZ domain in MDCK cells disturbs the cell-cell contact-induced junctional localization of tight junction proteins, as well as inhibiting TER development. Furthermore, the binding of Cdc42:GTP to the CRIB/PDZ domain of PAR-6 enhances the kinase activity of PAR-6-bound aPKC. Detailed analyses suggest that the binding of PAR-6 to aPKC has the intrinsic potential to activate aPKC, which is only released when Cdc42:GTP binds to the CRIB/PDZ domain. CONCLUSION: The results indicate the involvement of PAR-6 in the aPKC function which is required for the cell-cell adhesion-induced formation of epithelial junctional structures, possibly through the cooperative regulation of aPKC activity with Cdc42.

Adaptor Proteins, Signal Transducing↗

PubMed1997

Decrease in the expression of a novel TGF beta1-inducible and ras-recision gene, TSC-36, in human cancer cells.

TSC-36, a TGF beta1-inducible gene, encodes a polypeptide that shows significant similarity to SPARC (secreted protein rich in cysteine), and follistatin, an activin-binding protein. The expression of the TSC-36 gene was reported to be extinguished in v-ras-transformed mouse fibroblastic cells, and also was found also to be abrogated in cells transformed with v-myc. The level of expression was, however, not affected in cells transformed with v-src, v-abl, or v-raf. The TSC-36 cDNA was first isolated from mouse cells, and recently its rat and human homologues have been reported which show striking similarity with each other. In various human tumor cells, TSC-36 mRNA was almost undetectable. TSC-36 mRNA was detected in various mouse organs, but its level was the highest in the lung. TSC-36 mRNA level was the highest in the lung among mouse organs, and on in situ hybridization, the TSC-36 transcript was detected in the alveolar epithelium but not in the bronchial epithelium. These features suggest possible usage of TSC-36 as one of the markers in human tumors.

3T3 Cells↗

PubMed1997

Induction of senescence-like phenotypes by forced expression of hic-5, which encodes a novel LIM motif protein, in immortalized human fibroblasts.

The hic-5 gene encodes a novel protein with Zn finger-like (LIM) motifs, the expression of which increases during cellular senescence. The ectopic expression of hic-5 in nontumorigenic immortalized human fibroblasts, whose expression levels of hic-5 were significantly reduced in comparison with those of mortal cells, decreased colony-forming efficiency. Stable clones expressing high levels of hic-5 mRNA showed higher levels of mRNAs for several extracellular matrix-related proteins, along with the alteration of an alternative splicing as seen in senescent cells and decreased c-fos inducibility. Furthermore, these clones acquired a senescence-like phenotype, such as growth retardation; senescence-like morphology; and increased expression of Cip1/WAF1/sdi1 after 20 to 40 population doublings. On the other hand, antisense RNA expression of hic-5 in human normal diploid fibroblasts delayed the senescence process. HIC-5 was localized in nuclei and had affinity for DNA. Based on these observations, we speculated that HIC-5 affected the expression of senescence-related genes through interacting with DNA and thereby induced the senescence-like phenotypes. To our knowledge, hic-5 is the first single gene that could induce senescence-like phenotypes in a certain type of immortalized human cell and mediate the normal process of senescence.

Alternative Splicing↗