Loss of Tumor Suppressor TMEM127 Drives Ret-Mediated Transformation Through Disrupted Membrane Dynamics

Internalization from the cell membrane and endosomal trafficking of receptor tyrosine kinases (RTKs) are important regulators of signaling in normal cells that can frequently be disrupted in cancer. The adrenal tumor pheochromocytoma (PCC) can be caused by activating mutations of the rearranged during transfection (RET) receptor tyrosine kinase, or inactivation of TMEM127, a transmembrane tumor suppressor implicated in trafficking of endosomal cargos. However, the role of aberrant receptor trafficking in PCC is not well understood. Here, we show that loss of TMEM127 causes wildtype RET protein accumulation on the cell surface, where increased receptor density facilitates constitutive ligand-independent activity and downstream signaling, driving cell proliferation. Loss of TMEM127 altered normal cell membrane organization and recruitment and stabilization of membrane protein complexes, impaired assembly, and maturation of clathrin-coated pits, and reduced internalization and degradation of cell surface RET. In addition to RTKs, TMEM127 depletion also promoted surface accumulation of several other transmembrane proteins, suggesting it may cause global defects in surface protein activity and function. Together, our data identify TMEM127 as an important determinant of membrane organization including membrane protein diffusability and protein complex assembly and provide a novel paradigm for oncogenesis in PCC where altered membrane dynamics promotes cell surface accumulation and constitutive activity of growth factor receptors to drive aberrant signaling and promote transformation

Evolutionary analysis of endopolygalacturonase encoding genes of Botrytis cinerea

Sequence analysis of five of the six endopolygalacturonase-encoding genes (Bcpg1, Bcpg2, Bcpg3, Bcpg4, Bcpg5) from 32 strains of Botrytis cinerea showed marked gene to gene differences in the amount of among-strains diversity. Bcpg4 was almost invariable in all strains; Bcpg3 and Bcpg5 showed a moderate variability, similar to that of non-pathogenicity-associated genes examined in other studies. Conversely, Bcpg1 and Bcpg2 were highly variable and were shown to be under positive selection based on the McDonald-Kreitman test and likelihood ratio test. The evolution of the five endopolygalacturonase genes is explained by their different ecophysiological role. Diversification and balancing selection, as detected in Bcpg1 and Bcpg2, can be used by the pathogen to escape recognition by the host and delay plant reaction in the early phases of infection. The analysis of the polymorphisms and the location of the sites with high probability of being positively selected highlighted the relevance of variability of the BcPG1 and BcPG2 proteins at their C-terminal end. By contrast, the absence of variability in Bcpg4 suggests that the efficiency of the product of this gene is critical for B. cinerea growth in late phases of infection or during intraspecific competition, thus markedly affecting strain fitness

An endopolygalacturonase gene of Diaporthe helianthi

In an attempt to define virulence determinants of Diaporthe helianthi, the causative agent of sunflower stem canker, the gene named Dhpg, coding for an endopolygalacturonase, was investigated in the highly virulent strain 8/96 isolated from a diseased plant in France. The 1130 bp coding sequence, in addition to 1473 bp from the upstream region, were cloned, sequenced and analyzed. Dhpg was most closely related to polygalacturonase genes from phytopathogenic fungi, such as Ophiostoma ulmi, O. novo-ulmi, and Gibberella zeae. A Southern blot RFLP analysis proved that Dhpg was represented in single-copy in the genome of the isolate 8/96. Analyses carried out both in vitro on liquid cultures and in vivo on host infected tissues provided evidence of the constitutive expression of the Dhpg transcript under all tested conditions. Moreover, an European collection of D. helianthi isolates was screened for the presence of Dhpg homologues by PCR, revealing the same single band in all French and Yugoslavian isolates, while one Romanian and all Italian isolates displayed a variable pattern. This genetic variability related to the different geographic origin of D. helianthi is consistent with data previously reported for different loci on the same set of isolates. This is the first report of a polygalacturonase gene in D. helianthi

An endopolygalacturonese gene of Diaporthe helianthi

In the attempt of defining virulence determinants of Diaporthe helianthi, the causative agent of sunflower stem canker, the gene named Dhpg, coding for an endopolygalacturonase, was investigated in the highly virulent strain 8/96 isolated from a diseased plant in France. The 1624 bp coding sequence, in addition to 1343 bp from the upstream region, were cloned, sequenced and analyzed. Dhpg was most closely related to polygalacturonase genes from phytopathogenic fungi, such as Ophiostoma ulmi, O. novo-ulmi, and Gibberella zeae. A Southern blot RFLP analysis proved that Dhpg was represented in single-copy in the genome of the isolate 8/96. Analyses carried out both in vitro on liquid cultures and in vivo on host infected tissues provided evidence of the constitutive expression of the Dhpg transcript under all tested conditions. Moreover, an European collection of D. helianthi isolates was screened for the presence of Dhpg homologues by PCR, revealing the same single band in all French and Yugoslavian isolates, while one Romanian and all Italian isolates displayed a variable pattern. This genetic variability related to the different D. helianthi geographic origin is consistent with data previously reported for different loci on the same set of isolates. This is the first report concerning a polygalacturonase gene in D. helianthi