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Squamous cell carcinoma–related oncogene (SCCRO, also known as DCUN1D1) is a component of the E3 for neddylation. As such, DCUN1D1 regulates the neddylation of cullin family members. Targeted inactivation of DCUN1D1 in mice results in male-specific infertility. Infertility in DCUN1D1-/- mice is secondary to primary defects in spermatogenesis. Time-dam experiments mapped the onset of the defect in spermatogenesis to 5.5 to 6 weeks of age, which temporally corresponds to defects in spermiogenesis. Although the first round of spermatogenesis progressed normally, the number of spermatozoa released into the seminiferous lumen and epididymis of DCUN1D1-/- mice was significantly reduced. Spermatozoa in DCUN1D1-/- mice had multiple abnormalities, including globozoospermia, macrocephaly, and multiple flagella. Many of the malformed spermatozoa in DCUN1D1-/- mice were multinucleated, with supernumerary and malpositioned centrioles, suggesting a defect in the resolution of intercellular bridges. The onset of the defect in spermatogenesis in DCUN1D1-/- mice corresponds to an increase in DCUN1D1 expression observed during normal spermatogenesis. Moreover, consistent with its known function as a component of the E3 in neddylation, the pattern of DCUN1D1 expression temporally correlates with an increase in the neddylated cullin fraction and stage-specific increases in the total ubiquitinated protein pool in wild-type mice. Levels of neddylated Cul3 were decreased in DCUN1D1-/- mice, and ubiquitinated proteins did not accumulate during the stages in which DCUN1D1 expression peaks during spermatogenesis in wild-type mice. Combined, these findings suggest that DCUN1D1-/- mice fail to release mature spermatozoa into the seminiferous lumen, possibly due to unresolved intercellular bridges. Furthermore, the effects of DCUN1D1 on spermatogenesis likely involve its regulation of cullin-RING-ligase (CRL)–type ubiquitin E3 activity during spermiogenesis through its role in promoting Cul3 neddylation. The specific CRLs required for spermiogenesis and their protein targets require identification. [ABSTRACT FROM AUTHOR]

Tunneling nanotubes are long, non-adherent F-actin-based cytoplasmic extensions which connect proximal or distant cells and facilitate intercellular transfer. The identification of nanotubes has been limited to cell lines, and their role in cancer remains unclear. We detected tunneling nanotubes in mesothelioma cell lines and primary human mesothelioma cells. Using a low serum, hyperglycemic, acidic growth medium, we stimulated nanotube formation and bidirectional transfer of vesicles, proteins, and mitochondria between cells. Notably, nanotubes developed between malignant cells or between normal mesothelial cells, but not between malignant and normal cells. Immunofluorescent staining revealed their actinbased assembly and structure. Metformin and an mTor inhibitor, Everolimus, effectively suppressed nanotube formation. Confocal microscopy with 3-dimensional reconstructions of sectioned surgical specimens demonstrated for the first time the presence of nanotubes in human mesothelioma and lung adenocarcinoma tumor specimens. We provide the first evidence of tunneling nanotubes in human primary tumors and cancer cells and propose that these structures play an important role in cancer cell pathogenesis and invasion. [ABSTRACT FROM AUTHOR]

Tunneling nanotubes are long, non-adherent F-actin-based cytoplasmic extensions which connect proximal or distant cells and facilitate intercellular transfer. The identification of nanotubes has been limited to cell lines, and their role in cancer remains unclear. We detected tunneling nanotubes in mesothelioma cell lines and primary human mesothelioma cells. Using a low serum, hyperglycemic, acidic growth medium, we stimulated nanotube formation and bidirectional transfer of vesicles, proteins, and mitochondria between cells. Notably, nanotubes developed between malignant cells or between normal mesothelial cells, but not between malignant and normal cells. Immunofluorescent staining revealed their actin-based assembly and structure. Metformin and an mTor inhibitor, Everolimus, effectively suppressed nanotube formation. Confocal microscopy with 3-dimensional reconstructions of sectioned surgical specimens demonstrated for the first time the presence of nanotubes in human mesothelioma and lung adenocarcinoma tumor specimens. We provide the first evidence of tunneling nanotubes in human primary tumors and cancer cells and propose that these structures play an important role in cancer cell pathogenesis and invasion.