Inhibition of Anchorage-independent Growth of Transformed NIH3T3 Cells by Epithelial Protein Lost in Neoplasm (EPLIN) Requires Localization of EPLIN to Actin Cytoskeleton

Abstract

Epithelial protein lost in neoplasm (EPLIN) is a cytoskeleton-associated protein characterized by the presence of a single centrally located lin-11, isl-1, and mec-3 (LIM) domain. We have reported previously that EPLIN is down-regulated in transformed cells. In this study, we have investigated whether ectopic expression of EPLIN affects transformation. In untransformed NIH3T3 cells, retroviral-mediated transduction of EPLIN did not alter the cell morphology or growth. NIH3T3 cells expressing EPLIN, however, failed to form colonies when transformed by the activated Cdc42 or the chimeric nuclear oncogene EWS/Fli-1. This suppression of anchorage-independent growth was not universal because EPLIN failed to inhibit the colony formation of Ras-transformed cells. Interestingly, the localization of EPLIN to the actin cytoskeleton was maintained in the EWS/Fli-1- or Cdc42-transformed cells, but not in Ras-transformed cells where it was distributed heterogeneously in the cytoplasm. Using truncated EPLIN constructs, we demonstrated that the NH(2)-terminal region of EPLIN is necessary for both the localization of EPLIN to the actin cytoskeleton and suppression of anchorage-independent growth of EWS/Fli-1-transformed cells. The LIM domain or the COOH-terminal region of EPLIN could be deleted without affecting its cytoskeletal localization or ability to suppress anchorage-dependent growth. Our study indicates EPLIN may function in growth control by associating with and regulating the actin cytoskeleton.

ZNF185, an actin–cytoskeleton-associated growth inhibitory LIM protein in prostate cancer

“…In addition, some LIM domain-containing proteins are also involved in pathological processes such as oncogenesis (e.g. EPLIN, Testin and LMO4) (Maul and Chang, 1999;Tatarelli et al, 2000;Tobias et al, 2001;Visvader et al, 2001;Song et al, 2002;Sum et al, 2002;Garvalov et al, 2003). As the full-length ZNF185 cDNA has not been experimentally cloned, the biological function of this LIM domain-containing protein and the pathological relevance in PCa is unknown.…”

Epidermal Growth Factor Promotes Protein Degradation of Epithelial Protein Lost in Neoplasm (EPLIN), a Putative Metastasis Suppressor, during Epithelial-mesenchymal Transition

“…Two EPLIN isoforms, the 600-residue EPLIN-␣ and 759-residue EPLIN-␤, are expressed in epithelial and endothelial cells in a context-dependent manner (11)(12)(13)15). EPLIN was initially thought to be a potential tumor suppressor that is preferentially expressed in human epithelia but frequently lost in cancerous cells (11,16). Recently, we reported a novel role of EPLIN in the regulation of EMT and invasiveness (17).…”

Conversion of the LIMA1 tumour suppressor into an oncogenic LMO-like protein by API2–MALT1 in MALT lymphoma

“…While API2-MALT1 cleaves NIK, a regulator of the non-canonical NF-kB signalling pathway 37 , our current demonstration of LIMA1a proteolysis by API2-MALT1 represents the first evidence of a paracaspase-mediated mechanism wherein a wild-type tumour suppressor is cleaved to produce a proteolytic fragment that exhibits its own autonomous oncogenic activity. LIMA1 is a cytoskeleton-associated protein encoded by a gene on band 12q13 and contains a single centrally located lin-11, isl-1 and mec-3 (LIM) domain, flanked by two actin-binding domains each located at the N-and C termini of the wild-type protein 58 . LIMA1 has been recognized as a tumour suppressor based on the multiple mechanisms by which it is targeted for inactivation 40,42,44,59 .…”

“…Further, expression of LIMA1 has been demonstrated to suppress anchorage-independent growth 58 . The biological significance of LIMA1 in cancer is underscored by the fact that loss of expression of LIMA1 in various cancers is correlated with adverse clinical outcomes and inferior survival 37,39,41 .…”