Proteostatic Remodeling of Small Heat Shock Chaperones─Crystallins by Ran-Binding Protein 2─and the Peptidyl-Prolyl cis–trans Isomerase and Chaperone Activities of Its Cyclophilin Domain
Hemangi Patil, Haiqing Yi, Kyoung-in Cho and Paulo A. Ferreira*,
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引用次数: 0
Abstract
Disturbances in protein phase transitions promote protein aggregation─a neurodegeneration hallmark. The modular Ran-binding protein 2 (Ranbp2) is a cytosolic molecular hub for rate-limiting steps of phase transitions of Ran-GTP-bound protein ensembles exiting nuclear pores. Chaperones also regulate phase transitions and proteostasis by suppressing protein aggregation. Ranbp2 haploinsufficiency promotes the age-dependent neuroprotection of the chorioretina against phototoxicity by proteostatic regulations of neuroprotective substrates of Ranbp2 and by suppressing the buildup of polyubiquitylated substrates. Losses of peptidyl-prolyl cis–trans isomerase (PPIase) and chaperone activities of the cyclophilin domain (CY) of Ranbp2 recapitulate molecular effects of Ranbp2 haploinsufficiency. These CY impairments also stimulate deubiquitylation activities and phase transitions of 19S cap subunits of the 26S proteasome that associates with Ranbp2. However, links between CY moonlighting activity, substrate ubiquitylation, and proteostasis remain incomplete. Here, we reveal the Ranbp2 regulation of small heat shock chaperones─crystallins in the chorioretina by proteomics of mice with total or selective modular deficits of Ranbp2. Specifically, loss of CY PPIase of Ranbp2 upregulates αA-Crystallin, which is repressed in adult nonlenticular tissues. Conversely, impairment of CY’s chaperone activity opposite to the PPIase pocket downregulates a subset of αA-Crystallin’s substrates, γ-crystallins. These CY-dependent effects cause age-dependent and chorioretinal-selective declines of ubiquitylated substrates without affecting the chorioretinal morphology. A model emerges whereby inhibition of Ranbp2’s CY PPIase remodels crystallins’ expressions, subdues molecular aging, and preordains the chorioretina to neuroprotection by augmenting the chaperone capacity and the degradation of polyubiquitylated substrates against proteostatic impairments. Further, the druggable Ranbp2 CY holds pan-therapeutic potential against proteotoxicity and neurodegeneration.
期刊介绍:
ACS Chemical Neuroscience publishes high-quality research articles and reviews that showcase chemical, quantitative biological, biophysical and bioengineering approaches to the understanding of the nervous system and to the development of new treatments for neurological disorders. Research in the journal focuses on aspects of chemical neurobiology and bio-neurochemistry such as the following:
Neurotransmitters and receptors
Neuropharmaceuticals and therapeutics
Neural development—Plasticity, and degeneration
Chemical, physical, and computational methods in neuroscience
Neuronal diseases—basis, detection, and treatment
Mechanism of aging, learning, memory and behavior
Pain and sensory processing
Neurotoxins
Neuroscience-inspired bioengineering
Development of methods in chemical neurobiology
Neuroimaging agents and technologies
Animal models for central nervous system diseases
Behavioral research