Fibronectin rescues estrogen receptor α from lysosomal degradation in breast cancer cells

Estrogen receptor α (ERα) is expressed in tissues as diverse as brains and mammary glands. In breast cancer, ERα is a key regulator of tumor progression. Therefore, understanding what activates ERα is critical for cancer treatment in particular and cell biology in general. Using biochemical approaches and superresolution microscopy, we show that estrogen drives membrane ERα into endosomes in breast cancer cells and that its fate is determined by the presence of fibronectin (FN) in the extracellular matrix; it is trafficked to lysosomes in the absence of FN and avoids the lysosomal compartment in its presence. In this context, FN prolongs ERα half-life and strengthens its transcriptional activity. We show that ERα is associated with β1-integrin at the membrane, and this integrin follows the same endocytosis and subcellular trafficking pathway triggered by estrogen. Moreover, ERα+ vesicles are present within human breast tissues, and colocalization with β1-integrin is detected primarily in tumors. Our work unravels a key, clinically relevant mechanism of microenvironmental regulation of ERα signaling.Fil: Sampayo, Rocío Guadalupe. Universidad Nacional de San Martin. Instituto de Nanosistemas; Argentina. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Oncología "Ángel H. Roffo"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Toscani, Andrés Martin. Universidad Nacional de Luján; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Rubashkin, Matthew G.. University of California; Estados UnidosFil: Thi, Kate. Lawrence Berkeley National Laboratory; Estados UnidosFil: Masullo, Luciano Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Violi, Ianina Lucila. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones en Bionanociencias "Elizabeth Jares Erijman"; ArgentinaFil: Lakins, Jonathon N.. University of California; Estados UnidosFil: Caceres, Alfredo Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra. Universidad Nacional de Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra; ArgentinaFil: Hines, William C.. Lawrence Berkeley National Laboratory; Estados UnidosFil: Coluccio Leskow, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; Argentina. Universidad Nacional de Luján; ArgentinaFil: Stefani, Fernando Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Chialvo, Dante Renato. Universidad de Buenos Aires; Argentina. Universidad Nacional de San Martín. Escuela de Ciencia y Tecnología. Centro Internacional de Estudios Avanzados; ArgentinaFil: Bissell, Mina J.. Lawrence Berkeley National Laboratory; Estados UnidosFil: Weaver, Valerie M.. University of California; Estados UnidosFil: Simian, Marina. Universidad Nacional de San Martin. Instituto de Nanosistemas; Argentina. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Oncología "Ángel H. Roffo"; Argentin

Mutational spectrum of the SPG4 (SPAST) and SPG3A (ATL1) genes in Spanish patients with hereditary spastic paraplegia

<p>Abstract</p> <p>Background</p> <p>Hereditary Spastic Paraplegias (HSP) are characterized by progressive spasticity and weakness of the lower limbs. At least 45 loci have been identified in families with autosomal dominant (AD), autosomal recessive (AR), or X-linked hereditary patterns. Mutations in the <it>SPAST </it>(<it>SPG4</it>) and <it>ATL1 </it>(<it>SPG3A</it>) genes would account for about 50% of the ADHSP cases.</p> <p>Methods</p> <p>We defined the <it>SPAST </it>and <it>ATL1 </it>mutational spectrum in a total of 370 unrelated HSP index cases from Spain (83% with a pure phenotype).</p> <p>Results</p> <p>We found 50 <it>SPAST </it>mutations (including two large deletions) in 54 patients and 7 <it>ATL1 </it>mutations in 11 patients. A total of 33 of the <it>SPAST </it>and 3 of the <it>ATL1 </it>were new mutations. A total of 141 (31%) were familial cases, and we found a higher frequency of mutation carriers among these compared to apparently sporadic cases (38% vs. 5%). Five of the <it>SPAST </it>mutations were predicted to affect the pre-mRNA splicing, and in 4 of them we demonstrated this effect at the cDNA level. In addition to large deletions, splicing, frameshifting, and missense mutations, we also found a nucleotide change in the stop codon that would result in a larger ORF.</p> <p>Conclusions</p> <p>In a large cohort of Spanish patients with spastic paraplegia, <it>SPAST </it>and <it>ATL1 </it>mutations were found in 15% of the cases. These mutations were more frequent in familial cases (compared to sporadic), and were associated with heterogeneous clinical manifestations.</p

Transcriptional and Post-Transcriptional Regulation of SPAST, the Gene Most Frequently Mutated in Hereditary Spastic Paraplegia

Hereditary spastic paraplegias (HSPs) comprise a group of neurodegenerative disorders that are characterized by progressive spasticity of the lower extremities, due to axonal degeneration in the corticospinal motor tracts. HSPs are genetically heterogeneous and show autosomal dominant inheritance in ∼70–80% of cases, with additional cases being recessive or X-linked. The most common type of HSP is SPG4 with mutations in the SPAST gene, encoding spastin, which occurs in 40% of dominantly inherited cases and in ∼10% of sporadic cases. Both loss-of-function and dominant-negative mutation mechanisms have been described for SPG4, suggesting that precise or stoichiometric levels of spastin are necessary for biological function. Therefore, we hypothesized that regulatory mechanisms controlling expression of SPAST are important determinants of spastin biology, and if altered, could contribute to the development and progression of the disease. To examine the transcriptional and post-transcriptional regulation of SPAST, we used molecular phylogenetic methods to identify conserved sequences for putative transcription factor binding sites and miRNA targeting motifs in the SPAST promoter and 3′-UTR, respectively. By a variety of molecular methods, we demonstrate that SPAST transcription is positively regulated by NRF1 and SOX11. Furthermore, we show that miR-96 and miR-182 negatively regulate SPAST by effects on mRNA stability and protein level. These transcriptional and miRNA regulatory mechanisms provide new functional targets for mutation screening and therapeutic targeting in HSP

Evaluation of loss of function as an explanation for SPG4-based hereditary spastic paraplegia

The spectrum of mutations (missense, non-sense and splice-site) associated with hereditary spastic paraplegia 4 (HSP-SPG4) (SPG4:OMIM#182601) has suggested that this autosomal dominant disease results from loss of function. Because the protein encoded by SPG4, termed spastin, is a microtubule-severing enzyme, a loss-of-function scenario for the disease suggests that corticospinal axons degenerate due to inadequate microtubule severing resulting from inactivation of one spastin allele. Lending more complexity to the situation, there are two major isoforms of spastin (M1 and M87) translated from two start codons. M87 is widely expressed, while M1 is appreciably detected only in adult spinal cord. Here, we focused on four HSP-associated mutations of the SPG4 gene located outside of the AAA region essential for microtubule severing. We found that none of these mutations affected the enzymatic activity or expression levels of either M1 or M87. Three of the mutations resulted in dominant-negative activity of M1. Surprisingly, the S44L mutation, which is asymptomatic when present heterozygously, conferred dominant-negative activity, while the E112K mutation, which is symptomatic when present heterozygously, did not. Clinical symptoms reported for patients carrying the dominant-negative mutations L195V or 46Stop are not more severe than those reported for patients carrying the non-dominant-negative E112K mutation. These results indicate that there are cases of HSP-SPG4 that cannot be explained by insufficient spastin microtubule-severing activity

Evaluation of loss of function as an explanation for SPG4-based hereditary spastic paraplegia

The spectrum of mutations (missense, non-sense and splice-site) associated with hereditary spastic paraplegia 4 (HSP-SPG4) (SPG4:OMIM#182601) has suggested that this autosomal dominant disease results from loss of function. Because the protein encoded by SPG4, termed spastin, is a microtubule-severing enzyme, a loss-of-function scenario for the disease suggests that corticospinal axons degenerate due to inadequate microtubule severing resulting from inactivation of one spastin allele. Lending more complexity to the situation, there are two major isoforms of spastin (M1 and M87) translated from two start codons. M87 is widely expressed, while M1 is appreciably detected only in adult spinal cord. Here, we focused on four HSP-associated mutations of the SPG4 gene located outside of the AAA region essential for microtubule severing. We found that none of these mutations affected the enzymatic activity or expression levels of either M1 or M87. Three of the mutations resulted in dominant-negative activity of M1. Surprisingly, the S44L mutation, which is asymptomatic when present heterozygously, conferred dominant-negative activity, while the E112K mutation, which is symptomatic when present heterozygously, did not. Clinical symptoms reported for patients carrying the dominant-negative mutations L195V or 46Stop are not more severe than those reported for patients carrying the non-dominant-negative E112K mutation. These results indicate that there are cases of HSP-SPG4 that cannot be explained by insufficient spastin microtubule-severing activity