PubMed · 12594497
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R John Ellis. 2003-02-20. Molecular chaperones: Plugging the transport gap.. https://doi.org/10.1038/421801a
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Protein quality control (PQC) is carried out in part by the chaperone Hsp70 in concert with adapters of the J-domain protein (JDP) family. The JDPs, also called Hsp40s, are thought to recruit Hsp70 into complexes with specific client proteins. However, the molecular principles regulating this process are not well understood. We describe the de novo design of Hsp70 binding proteins that either inhibit or stimulate Hsp70 ATPase activity. An ATPase stimulating design promoted the refolding of denatured luciferase in vitro, similar to native JDPs. Targeting of this design to intracellular condensates resulted in their nearly complete dissolution and revealed roles as cell growth promoting signaling hubs. The designs inform our understanding of chaperone structure-function relationships and provide a general and modular way to target PQC systems to regulate condensates and other cellular targets.
alpha-Synuclein (AS) is a main component of Lewy bodies in midbrain dopamine neurons pathologically characteristic of Parkinson's disease. We show that heat shock protein (Hsp) 70 inhibits AS fibril formation via preventing the formation of prefibrillar AS (PreAS), binding with PreAS to impede nuclei formation, and binding with nuclei to retard fibril elongation. Also, Hsp70 suppresses the PreAS-induced permeabilization of vesicular membrane through interactions with PreAS. The substrate-binding domain alone is sufficient for Hsp70 to inhibit AS fibril formation. The binding of Hsp70 with PreAS only requires the substrate-binding subdomain, and the binding with AS nuclei requires the C-terminal lid subdomain as well. The results may form the molecular basis for elucidating the mechanism of AS fibril formation and the crucial roles of chaperones in protecting proteins from toxic conversion in many conformational diseases.
OBJECTIVE: To study the clinical features and molecular genetics of acute monocytic leukemia (AML) after orthotopic liver transplantation and significance thereof. METHODS: The clinical manifestations, laboratory findings, development, diagnosis, treatment, and prognosis of the first case of AML after orthotopic liver transplantation in the world, a Chinese, male, aged 46, were observed. RT-PCR was used to analyze the mRNA expression of FLT3, Pim-1, and Hsp-70 in the bone marrow mononuclear cells (BMMCs) of the patient. Nucleotide sequence analysis was used to detect the mutation of FLT3-ITD. Flow cytometry was used to examine the protein expression of C-kit, a stem cell factor receptor, and platelet derived growth factor receptor-alpha (PDGFRalpha). RESULTS: (1) Three months after the orthotopic liver transplantation the patient manifested symptoms and signs of anemia and thrombocytopenia. Laboratory tests found increase of white blood cells and myeloblasts with Auer's rods. Cytogenetic analysis showed a genotype of 46XY/47XY with an extra chromosome 8. Bone marrow examination revealed increased promonocytes. The diagnosis of chronic myelomonocytic leukemia was made. Five months after the liver transplantation the disease developed to AML. The patient underwent combined chemotherapy (HA or DA regimens) for 5 courses and showed a partial remission both hematologically and in bone marrow examination at first, however, became resistant to all chemotherapeutic agents. RT-PCR showed absence of wild type FLT3 allele. At last the patient died of infection. (2) A FLT3-ITD mutation of "insertion" type was identified in the BMMCs. The Pim-1 mRNA was weakly expressed and the expression of Hsp-70 mRNA was upregulated in the BMMCs. (3) The protein expression of C-kit and that of PDGFRalpha were both upregulated in the BMMCs as showed by flow cytometry. CONCLUSION: Orthotopic liver transplantation may be complicated with acute leukemia heterogeneous in clinical features and hematology. Certain defects in cytogenetics/molecular genetics may attribute to unfavorable prognosis.