RESUMEN
Cell secretion repairs tissue damage and restores homeostasis throughout adult life. The extracellular heat shock protein-90alpha (eHsp90α) has been reported as an exosome cargo and a potential driver of wound healing. However, neither the mechanism of secretion nor the genetic evidence for eHsp90α in wound healing has been substantiated. Herein, we show that tissue injury causes massive deposition of eHsp90α in tissues and secretion of eHsp90α by cells. Sequential centrifugations of conditioned medium from relevant cell lines revealed the relative distributions of eHsp90α in microvesicle, exosome and trypsin-sensitive supernatant fractions to be approximately <2%, <4% and >95%, respectively. Establishing the cell-number-to-interstitial-fluid-volume (CIF) ratio for the microenvironment of human tissues as 1 × 109 cells: 1 mL interstitial fluid enabled us to predict the corresponding tissue concentrations of eHsp90α in these fractions as 3.74 µg/mL, 5.61 µg/mL and 178 µg/mL. Remarkably, the 178 µg/mL eHsp90α matches the previously reported 100-300 µg/mL of recombinant eHsp90α whose topical application promotes maximum wound healing in animal models. More importantly, we demonstrate that two parallel secretory autophagy-regulating gene families, the autophagy-regulating (AR) genes and the Golgi reassembly-stacking protein (GRASP) genes work together to mediate the secretion of the physiological concentration of eHsp90α to promote wound healing. Thus, utilization of the CIF ratio-based extrapolation method may enable investigators to rapidly predict biomarker targets from cell-conditioned-medium data.
Asunto(s)
Autofagia , Líquido Extracelular , Proteínas HSP90 de Choque Térmico , Cicatrización de Heridas , Humanos , Proteínas HSP90 de Choque Térmico/metabolismo , Animales , Líquido Extracelular/metabolismo , Ratones , Vías Secretoras , Masculino , Exosomas/metabolismo , Línea CelularRESUMEN
BACKGROUND: Recessive dystrophic epidermolysis bullosa (RDEB) is an incurable widespread blistering skin disorder caused by mutations in the gene encoding for type VII collagen (C7), the major component of anchoring fibrils. OBJECTIVES: To evaluate the efficacy and safety of intravenous (IV) gentamicin readthrough therapy in patients with RDEB harbouring nonsense mutations. The primary outcomes were increased expression of C7 in patients' skin and safety assessments (ototoxicity, nephrotoxicity, autoimmune response); secondary outcomes included measuring wound healing in target wounds and assessment by a validated Epidermolysis Bullosa Disease Activity and Scarring Index (EBDASI) scoring system. METHODS: An open-label pilot trial to assess two different IV gentamicin regimens between August 2018 and March 2020 with follow-up through to 180â days post-treatment was carried out. Three patients with RDEB with confirmed nonsense mutations in COL7A1 in either one or two alleles and decreased baseline expression of C7 at the dermal-epidermal junction (DEJ) of their skin participated in the study. Three patients received gentamicin 7.5â mg kg-1 daily for 14â days and two of the three patients further received 7.5â mg kg-1 IV gentamicin twice weekly for 12 weeks. Patients who had pre-existing auditory or renal impairment, were currently using ototoxic or nephrotoxic medications, or had allergies to aminoglycosides or sulfate compounds were excluded. RESULTS: After gentamicin treatment, skin biopsies from all three patients (age range 18-28â years) exhibited increased C7 in their DEJ. With both regimens, the new C7 persisted for at least 6â months post-treatment. At 1 and 3â months post-treatment, 100% of the monitored wounds exhibited > 85% closure. Both IV gentamicin infusion regimens decreased EBDASI total activity scores. Of the patients assessed with the EBDASI, all exhibited decreased total activity scores 3â months post-treatment. All three patients completed the study; no adverse effects or anti-C7 antibodies were detected. CONCLUSIONS: IV gentamicin induced the readthrough of nonsense mutations in patients with RDEB and restored functional C7 in their skin, enhanced wound healing and improved clinical parameters. IV gentamicin may be a safe, efficacious, low-cost and readily available treatment for this population of patients with RDEB.
Recessive dystrophic epidermolysis bullosa (RDEB) is a rare and life-threatening inherited skin disease that causes widespread skin blisters that heal with scarring. RDEB affects around 1 in every 100,000 individuals globally. The condition is caused by a mutation in the gene coding for type VII collagen (C7), resulting in a deficiency of C7. C7 is a vital component of the skin as it is responsible for holding the skin's upper two layers together. To date, there are no approved systemic treatments that can cure RDEB. This study, from the United States, aimed to evaluate the effectiveness and safety of intravenous (medicine delivered directly into a patient's vein) gentamicin (an antibiotic) for people with RDEB who have nonsense mutations in their genes (a type of mutation that prevents the production of complete proteins by introducing an inappropriate 'stop signal'). We gave gentamicin to three patients with RDEB every day for 14â days, and two of the three patients further received intravenous gentamicin twice a week for 12 weeks. After gentamicin treatment, all three patients showed increased expression of C7. With both regimens, the new C7 stayed for at least 6â months after the treatment. At 1 and 3â months after treatment, 100% of the wounds being monitored in the patients had closed by more than 85%. All three patients completed the study, and no side-effects were experienced. In conclusion, intravenous gentamicin increased the production of C7 and improved wound healing and quality of life in patients with RDEB carrying nonsense mutations. Intravenous gentamicin may offer a safe, effective, low-cost and readily available therapy in patients with RDEB.
Asunto(s)
Codón sin Sentido , Colágeno Tipo VII , Epidermólisis Ampollosa Distrófica , Gentamicinas , Humanos , Gentamicinas/administración & dosificación , Gentamicinas/efectos adversos , Epidermólisis Ampollosa Distrófica/tratamiento farmacológico , Epidermólisis Ampollosa Distrófica/genética , Colágeno Tipo VII/genética , Colágeno Tipo VII/inmunología , Proyectos Piloto , Masculino , Femenino , Adulto , Adolescente , Resultado del Tratamiento , Adulto Joven , Cicatrización de Heridas/efectos de los fármacos , Piel/patología , Piel/efectos de los fármacos , Antibacterianos/administración & dosificación , Antibacterianos/efectos adversos , Esquema de MedicaciónRESUMEN
Since the only and the milestone FDA approval of becaplermin gel (RegranexTM, 0.01% human recombinant PDGF-BB) as a (diabetic) wound healing therapeutic more than 25 years ago, no new therapeutic (excluding physical therapies, devices, dressings, anti-microbial agents, or other preventive treatments) for any type of wound healing has advanced to clinical applications. During the same period of time, the FDA has approved additional 250 new drugs for various human tumors, which were famously described as "wounds that do not heal". Two similar pathological conditions have experienced such a dramatic difference in therapeutics. More surprisingly, few in the wound healing community seem to be alarmed by this mysterious deficit. As it is often said, "damaging is far easier than re-building". In contrast to the primary duty of a cancer drug to damage a single molecule of the signaling network, a wound healing drug must be able to re-build the multi-level damages in the wound. No known single molecule alone is capable of repairing multi-cell-type and multi-pathway damages all at once. We argue that the previous single molecule-based strategy for developing wound healing therapeutics is profoundly flawed in theory. The future success of effective wound healing therapeutics requires a fundamental change in the paradigm.
Asunto(s)
Vendajes , Cicatrización de Heridas , Humanos , Proteínas Proto-Oncogénicas c-sis , Becaplermina/farmacologíaRESUMEN
Both COVID-19 and autoimmune bullous diseases represent potentially life-threatening conditions. Autoimmunity has been a special focus during the COVID-19 pandemic considering the possible detrimental mutual influence between COVID-19 and autoimmune disorders as well as their supposed induction or triggering by SARS-CoV-2 vaccines. There is a growing need to assess the impact of the current pandemic particularly in patients with autoimmune bullous diseases requiring potent and long-term immunosuppressive treatments. This review provides the relevant state-of-the-art knowledge, including our own research, about immunobullous diseases in relation to COVID-19 and summarizes expert perspectives on their management throughout the pandemic.
Asunto(s)
Enfermedades Autoinmunes , COVID-19 , Penfigoide Ampolloso , Pénfigo , Humanos , Vacunas contra la COVID-19 , Pandemias , COVID-19/epidemiología , SARS-CoV-2 , Enfermedades Autoinmunes/epidemiologíaRESUMEN
For decades, the undisputable definition of the cytosolic Hsp90α and hsp90ß proteins being evolutionarily conserved, ATP-driven chaperones has ruled basic research and clinical trials. The results of recent studies, however, have fundamentally challenged this paradigm, not to mention the spectacular failures of the paradigm-based clinical trials in cancer and beyond. We now know that Hsp90α and Hsp90ß are both ubiquitously expressed in all cell types but assigned for distinct and irreplaceable functions. Hsp90ß is essential during mouse development and Hsp90α only maintains male reproductivity in adult mice. Neither Hsp90ß nor Hsp90α could substitute each other under these biological processes. Hsp90ß alone maintains cell survival in culture and Hsp90α cannot substitute it. Hsp90α also has extracellular functions under stress and Hsp90ß does not. The dramatic difference in the steady-state expression of Hsp90 in different mouse organs is due to the variable expressions of Hsp90α. The lowest expression of Hsp90 is less than 2% and the highest expression of Hsp90 is 9% among non-transformed cell lines. The two linker regions only take up less than 5% of the Hsp90 proteins, but harbor 21% of the total amino acid substitutions, i.e., 40% in comparison to the 86% overall amino acid homology. A full understanding of the distinctions between Hsp90α and Hsp90ß could lead to new, safe and effective therapeutics targeting Hsp90 in human disorders such as cancer. This is the first comprehensive review of a comparison between the two cytosolic Hsp90 isoforms.
Asunto(s)
Proteínas HSP90 de Choque Térmico , Chaperonas Moleculares , Masculino , Ratones , Humanos , Animales , Chaperonas Moleculares/metabolismo , Proteínas HSP90 de Choque Térmico/metabolismo , Isoformas de Proteínas/metabolismo , Sustitución de AminoácidosRESUMEN
Tumor cells face constant stress of ischemic (nutrient paucity and hypoxia) environment when they migrate and invade too fast to outgrow the nearest blood vessels. During the temporary loss of support from circulation, the tumor cells must act self-sufficient to survive and then to migrate to re-connect with the nearest blood supply or die. We have previously reported that ablation of the low-density lipoprotein receptor-related protein 1 (LRP-1) completely nullified the ability of tumour cells to migrate and invade under serum-free conditions in vitro and to form tumours in vivo. The mechanism behind the important function by cell surface LRP-1 was not fully understood. Herein we show that LRP-1 orchestrates two parallel cell surface signalling pathways to support the full constitutive tumour cell migration. First, LRP-1 stabilizes activated epidermal growth factor receptor (EGFR) to contribute half of the pro-motility signalling. Second, LRP-1 mediates secreted Hsp90α autocrine signalling to bring the other half of pro-motility signalling. Only combined inhibitions of the EGFR signalling and the eHsp90α autocrine signalling led to the full blockade of the tumour cell migration as the LRP-1 depletion did. This finding uncovers a novel mechanism by which certain breast cancer cells use LRP-1 to engage parallel signalling pathways to move when they lose contact with blood support.
Asunto(s)
Neoplasias de la Mama , Movimiento Celular , Receptores ErbB/metabolismo , Femenino , Humanos , Proteína 1 Relacionada con Receptor de Lipoproteína de Baja Densidad/metabolismo , Transducción de SeñalRESUMEN
IMPORTANCE: Junctional epidermolysis bullosa (JEB) is an incurable blistering skin disorder with high infant mortality often caused by nonsense variants in the genes that encode laminin 332. OBJECTIVE: To evaluate the safety and outcomes following intravenous gentamicin readthrough therapy and subsequent laminin 332 expression in patients with JEB. DESIGN, SETTING, AND PARTICIPANTS: This open-label, pilot nonrandomized clinical trial assessed 1 course of low- or high-dose intravenous gentamicin, including follow-up at 30 and 90 days after treatment. Five pediatric patients with JEB (2 with intermediate JEB and 3 with severe JEB) and confirmed nonsense variants in LAMA3 or LAMB3 in 1 or 2 alleles and decreased expression of laminin 332 at the dermal-epidermal junction of their skin participated in the study, which was performed at a single institution in collaboration with physicians and home infusion services near the patients from April 1, 2019, to February 28, 2021, with follow-up until May 31, 2021. INTERVENTIONS: Three patients received gentamicin at 7.5 mg/kg daily for 14 days, and 2 patients received gentamicin at 10 mg/kg daily for 24 days. MAIN OUTCOMES AND MEASURES: Primary outcomes were change in expression of laminin 332 in patients' skin and assessments for safety (ototoxic effects, nephrotoxic effects, and autoimmune response). Secondary outcomes included wound healing in monitored wounds and Epidermolysis Bullosa Disease Activity and Scarring Index (EBDASI) score. RESULTS: After gentamicin treatment, all 5 patients (age range, 3 months to 10 years, 4 [80%] female) exhibited increased laminin 332 in the dermal-epidermal junction. By 1 month, 7 of 9 wounds in patients receiving low-dose intravenous gentamicin and all wounds in patients receiving high-dose intravenous gentamicin exhibited at least 50% wound closure. By 3 months, 8 of 9 wounds in patients receiving low-dose gentamicin and all wounds in patients receiving high-dose intravenous gentamicin exhibited greater than 85% closure. All 3 patients who were evaluated with EBDASI showed a decrease in total activity scores that met minimal clinically important differences 1 month after treatment. All 5 patients completed the study, and no ototoxic effects, nephrotoxic effects, or anti-laminin 332 antibodies were detected. CONCLUSIONS AND RELEVANCE: In this nonrandomized clinical trial, intravenous gentamicin therapy was associated with induced readthrough of nonsense variants in patients with JEB, restored functional laminin 332 in their skin, and wound closure during the 3-month study period. Although long-term safety and efficacy requires further evaluation, a single cycle of intravenous gentamicin may be a safe and readily available therapy in the short term for this population of patients with JEB. TRIAL REGISTRATION: ClinicalTrials.gov Identifiers: NCT03526159 and NCT04140786.
Asunto(s)
Epidermólisis Ampollosa de la Unión , Alelos , Niño , Epidermólisis Ampollosa de la Unión/tratamiento farmacológico , Epidermólisis Ampollosa de la Unión/genética , Femenino , Gentamicinas/metabolismo , Gentamicinas/uso terapéutico , Humanos , Lactante , Laminina , Masculino , Piel/metabolismo , Cicatrización de HeridasRESUMEN
IMPORTANCE: Epidermolysis bullosa simplex with muscular dystrophy (EBS-MD) is an autosomal recessive disorder caused by pathogenic variants in PLEC1, which encodes plectin. It is characterized by mild mucocutaneous fragility and blistering and muscle weakness. Translational readthrough-inducing drugs, such as repurposed aminoglycoside antibiotics, may represent a valuable therapeutic alternative for untreatable rare diseases caused by nonsense variants. OBJECTIVE: To evaluate whether systemic gentamicin, at a dose of 7.5 mg/kg/d for 14 consecutive days, is clinically beneficial in a patient with EBS-MD. DESIGN, SETTING, AND PARTICIPANTS: A single patient in Madrid, Spain, received 2 treatment courses with gentamicin on July 2019 and February 2020 with a follow-up period of 120 and 150 days, respectively. RESULTS: In this case report of a woman in her 30s with EBS-MD, before gentamicin treatment, the patient had mucocutaneous involvement, skeletal and respiratory muscle weakness, and myalgia that negatively affected her quality of life. Outcomes were evaluated with extensive laboratory tests and clinical scales. No nephrotoxic or ototoxic effects were detected after intravenous gentamicin administration. Gentamicin treatment was followed by plectin expression in the skin for at least 5 months. Although minimal changes were noted in skeletal muscle function (as measured by the Hammersmith functional motor scale and its expanded version: 6/40 to 7/40 and from 10/66 to 11/66, respectively) and respiratory musculature (maximal inspiratory and expiratory pressures D0 vs D16, MIP: 2.86 vs 3.63 KPa and MEP: 2.93 vs 4.63 KPa), myalgia disappeared (VAS dropped from 6 to 0), and quality of life improved (EuroQoL-5D-3L pain and anxiety dropped from 2 to 1). CONCLUSIONS AND RELEVANCE: The findings of this single case report suggest that gentamicin treatment may help suppress PLEC1 premature termination codons and induce plectin expression in EBS-MD primary keratinocytes and skin. Our study suggests that gentamicin may play an important role in treating EBS-MD owing to nonsense variants.
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Epidermólisis Ampollosa Simple , Distrofias Musculares , Epidermólisis Ampollosa Simple/complicaciones , Epidermólisis Ampollosa Simple/tratamiento farmacológico , Epidermólisis Ampollosa Simple/genética , Femenino , Gentamicinas/uso terapéutico , Humanos , Distrofias Musculares/complicaciones , Distrofias Musculares/diagnóstico , Distrofias Musculares/tratamiento farmacológico , Distrofia Muscular de Cinturas , Mialgia , Plectina/genética , Calidad de VidaRESUMEN
The rare capacity for heat shock protein 90 (Hsp90) chaperones to support almost the entire cellular signaling network was viewed as a potential breakthrough to combat tumor resistance to single-oncogene-based therapeutics. Over 2 decades, several generations of Hsp90 ATP binding inhibitors have entered numerous cancer clinical trials, but few have advanced to FDA approval for treatment of human cancers. Herein, we report that Hsp90 expression varies dramatically, especially among different types of noncancer cells and organs. The highly variable levels of Hsp90, from as low as 1.7% to as high as 9% of their total cellular proteins, were responsible for either an extreme sensitivity or an extreme resistance to a classical Hsp90 ATP-binding inhibitor. Among randomly selected cancer cell lines, the same client proteins for regulation of cell growth exhibited unexpectedly heterogenous reactions in response to an Hsp90 ATP-binding inhibitor, inconsistent with the current understanding. Finally, a minimum amount (<10%) of Hsp90ß was still required for client protein stability and cell survival even in the presence of full Hsp90α. These new findings of Hsp90 expression in host and isoform compensation in tumor cells could complicate biomarker selection, toxicity readout, and clinical efficacy of Hsp90-ATP-binding inhibitors in cancer clinical trials.
Asunto(s)
Antineoplásicos/farmacología , Proteínas HSP90 de Choque Térmico/efectos de los fármacos , Proteínas HSP90 de Choque Térmico/metabolismo , Neoplasias/tratamiento farmacológico , Isoformas de Proteínas/genética , Adenosina Trifosfato/metabolismo , Humanos , Chaperonas Moleculares/metabolismo , Neoplasias/metabolismo , Unión Proteica/efectos de los fármacosRESUMEN
Recessive dystrophic epidermolysis bullosa (RDEB) is a genetic skin blistering disease associated with progressive multiorgan fibrosis. RDEB is caused by biallelic mutations in COL7A1 encoding the extracellular matrix protein collagen VII (C7), which is necessary for epidermalâdermal adherence. C7 is not simply a structural protein but also has multiple functions, including the regulation of TGFß bioavailability and the inhibition of skin scarring. Intravenous (IV) administration of recombinant C7 (rC7) rescues C7-deficient mice from neonatal lethality. However, the effect on established RDEB has not been determined. In this study, we used small and large adult RDEB animal models to investigate the disease-modulating abilities of IV rC7 on established RDEB. In adult RDEB mice, rC7 accumulated at the basement membrane zone in multiple organs after a single infusion. Fortnightly IV injections of rC7 for 7 weeks in adult RDEB mice reduced fibrosis of skin and eye. The fibrosis-delaying effect was associated with a reduction of TGFß signaling. IV rC7 in adult RDEB dogs incorporated in the dermalâepidermal junction of skin and improved disease by promoting wound healing and reducing dermalâepidermal separation. In both species, IV C7 was well-tolerated. These preclinical studies suggest that repeated IV administration of rC7 is an option for systemic treatment of established adult RDEB.
Asunto(s)
Epidermólisis Ampollosa Distrófica , Animales , Colágeno Tipo VII/metabolismo , Perros , Epidermólisis Ampollosa Distrófica/tratamiento farmacológico , Epidermólisis Ampollosa Distrófica/genética , Epidermólisis Ampollosa Distrófica/metabolismo , Fibrosis , Ratones , Piel/patología , Factor de Crecimiento Transformador beta/metabolismoRESUMEN
BACKGROUND: Patients with recessive dystrophic epidermolysis bullosa (RDEB) lack functional type VII collagen (C7) leading to skin fragility, bullae, and erosive wounds. RDEB-Inversa (RDEB-I), a subset of RDEB, is characterized by lesions localized to body areas with higher skin temperatures such as flexures and skin folds. OBJECTIVE: We aimed to determine if C7 derived from RDEB-I mutations had structural and functional aberrancies that were temperature sensitive and could be reversed by lowering the temperature. METHODS: In this study, we generated 12 substitution mutations associated with RDEB-I via site-directed mutagenesis and purified recombinant C7 protein. These C7 mutants were evaluated for structural parameters (trimer formation and protease sensitivity) and the ability to promote keratinocyte migration at 37 °C (the temperature of skin folds) and 30 °C (the maximum skin temperature of arms and legs). Fibroblasts derived from RDEB-I patients were evaluated for C7 secretion and cellular migration at both temperatures. RESULTS: C7s from RDEB-I mutations exhibited decreased thermal stability, increased sensitivity to protease digestion, diminished formation of collagen trimers, and reduced ability to promote keratinocyte migration compared with wild-type C7. In addition, fibroblasts derived from RDEB-I patients demonstrated intracellular accumulation of C7 and abnormal cell migration at 37 °C. All of these aberrancies were corrected by reducing the temperature to 30 °C. C7s generated from severe-RDEB mutations (non-Inversa) did not display temperature-dependent perturbations. CONCLUSION: These data demonstrate that RDEB-I mutations generate C7 aberrancies that are temperature dependent. This may explain why RDEB-I patients develop clinical lesions in areas where their skin is considerably warmer.
Asunto(s)
Colágeno Tipo VII/genética , Colágeno Tipo VII/metabolismo , Epidermólisis Ampollosa Distrófica/genética , Temperatura , Línea Celular , Movimiento Celular/efectos de los fármacos , Colágeno Tipo VII/química , Colágeno Tipo VII/farmacología , Fibroblastos/fisiología , Humanos , Queratinocitos/fisiología , Estructura Molecular , Mutación , Péptido Hidrolasas/farmacología , Proteínas Recombinantes/química , Proteínas Recombinantes/farmacologíaRESUMEN
We study a patient with the human papilloma virus (HPV)-2-driven "tree-man" phenotype and two relatives with unusually severe HPV4-driven warts. The giant horns form an HPV-2-driven multifocal benign epithelial tumor overexpressing viral oncogenes in the epidermis basal layer. The patients are unexpectedly homozygous for a private CD28 variant. They have no detectable CD28 on their T cells, with the exception of a small contingent of revertant memory CD4+ T cells. T cell development is barely affected, and T cells respond to CD3 and CD2, but not CD28, costimulation. Although the patients do not display HPV-2- and HPV-4-reactive CD4+ T cells in vitro, they make antibodies specific for both viruses in vivo. CD28-deficient mice are susceptible to cutaneous infections with the mouse papillomavirus MmuPV1. The control of HPV-2 and HPV-4 in keratinocytes is dependent on the T cell CD28 co-activation pathway. Surprisingly, human CD28-dependent T cell responses are largely redundant for protective immunity.
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Antígenos CD28/deficiencia , Patrón de Herencia/genética , Papillomaviridae/fisiología , Piel/virología , Linfocitos T/inmunología , Adulto , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Antígenos CD28/genética , Antígenos CD28/metabolismo , Linfocitos T CD4-Positivos/inmunología , Niño , Endopeptidasas/metabolismo , Femenino , Genes Recesivos , Células HEK293 , Homocigoto , Humanos , Inmunidad Humoral , Memoria Inmunológica , Células Jurkat , Queratinocitos/patología , Masculino , Ratones Endogámicos C57BL , Oncogenes , Papiloma/patología , Papiloma/virología , Linaje , Señales de Clasificación de Proteína , ARN Mensajero/genética , ARN Mensajero/metabolismoRESUMEN
Hypoxia-inducible factor-1 (HIF-1), a master transcriptional factor for protecting cells from hypoxia, plays a critical role in spermatogenesis and tumorigenesis. For the past two decades, numerous small molecule inhibitors that block mRNA synthesis, protein translation, or DNA binding of HIF-1α have entered clinical trials. To date, few have advanced to FDA approval for clinical applications due to limited efficacy at their toxicity-tolerable dosages. New windows for developing effective and safe therapeutics require better understanding of the specific mechanism of action. The finding that a chaperone-defective mutant heat shock protein-90-alpha (Hsp90α) blocks spermatogenesis, a known hypoxia-driven process in mouse testis prompted us to focus on the role of Hsp90α in HIF-1α. Here we demonstrate that Hsp90α gene knockout causes a dramatic reduction of the high steady-state level of HIF-1α in the testis, blocking sperm production and causing infertility of the mice. In HIF-1α-dependent tumor cells, we found that Hsp90α forms protein complexes with hypoxia-elevated HIF-1α and Hsp90α knockout prevents hypoxia-induced HIF-1α accumulation. In contrast, downregulation of Hsp90ß had little effect on hypoxia-induced accumulation of HIF-1α. Instead, Hsp90ß protects signaling molecules responsible for cellular homeostasis from assault by 17-AAG (17-N-allylamino-17-demethoxygeldanamycin), a general ATPase inhibitor of both Hsp90α and Hsp90ß. Since targeting Hsp90ß gene is lethal in both cultured cells and in mice, our new finding explains the toxicity of the previous inhibitor trials and identifies the specific binding of Hsp90α to HIF-1α as a new therapeutic window for developing safer and more effective treatment of male infertility and cancer.