Localization of heat shock protein HSPA6 (HSP70B’) to sites of transcription in cultured differentiated human neuronal cells following thermal stress

Khalouei S, Chow AM, Brown IR

J. Neurochem. 2014 Dec;131(6):743-54

PMID: 25319762

Abstract

Heat shock proteins (Hsps) are a set of highly conserved proteins that are involved in cellular repair and protective mechanisms. In order to identify potential stress-sensitive sites in differentiated SH-SY5Y human neuronal cells, localization of two inducible members of the HSPA (HSP70) family was investigated, namely HSPA6 (HSP70B’) and HSPA1A (HSP70-1). Following heat shock, yellow fluorescent protein (YFP)-tagged HSPA6 and HSPA1A proteins localized to nuclear speckles that are enriched in RNA splicing factors (identified by SC35 and SON marker proteins) and then to the granular component of the nucleolus (identified by nucleophosmin). Subsequently, YFP-HSPA6 protein, but not YFP-HSPA1A, localized to the periphery of nuclear speckles that are sites of RNA transcription. The HSPA6 gene is present in the human genome but not in genomes of rat and mouse. Hence, current animal models of neurodegenerative diseases are lacking a potentially protective member of the HSPA family. Potential stress-sensitive sites were identified in differentiated human SH-SY5Y cells by the localization of HSPA6 (HSP70B’) and HSPA1A (HSP70-1) to nuclear components following heat shock. HSPA6 and HSPA1A rapidly moved to nuclear speckles, enriched in RNA splicing factors, then to the granular layer of the nucleolus. Subsequently, HSPA6 exhibited a novel localization not observed for the more widely studied HSPA1A, namely association with the periphery of nuclear speckles that are sites of transcription. HS = heat shock; HSPA6 = HSP70B’ protein; HSPA1A = HSP70-1 protein.

Heat shock response and homeostatic plasticity

Karunanithi S, Brown IR

Front Cell Neurosci 2015;9:68

PMID: 25814928

Abstract

Heat shock response and homeostatic plasticity are mechanisms that afford functional stability to cells in the face of stress. Each mechanism has been investigated independently, but the link between the two has not been extensively explored. We explore this link. The heat shock response enables cells to adapt to stresses such as high temperature, metabolic stress and reduced oxygen levels. This mechanism results from the production of heat shock proteins (HSPs) which maintain normal cellular functions by counteracting the misfolding of cellular proteins. Homeostatic plasticity enables neurons and their target cells to maintain their activity levels around their respective set points in the face of stress or disturbances. This mechanism results from the recruitment of adaptations at synaptic inputs, or at voltage-gated ion channels. In this perspective, we argue that heat shock triggers homeostatic plasticity through the production of HSPs. We also suggest that homeostatic plasticity is a form of neuroprotection.

Electrochemical immunosensors for effective evaluation of amyloid-beta modulators on oligomeric and fibrillar aggregation processes

Veloso AJ, Chow AM, Ganesh HV, Li N, Dhar D, Wu DC, Mikhaylichenko S, Brown IR, Kerman K

Anal. Chem. 2014 May;86(10):4901-9

PMID: 24784791

Abstract

A novel electrochemical immunosensor fabricated from gold compact disc electrodes was designed for rapid evaluation of aggregation processes that lead to the formation of oligomeric and fibrillar states of amyloid-beta(1-42) (Aβ(1-42)) during Alzheimer’s disease. Conformation-specific antibodies were immobilized on the surface of the gold electrode using a 3,3′-dithiobis (sulfosuccinimidyl) propionate (DTSSP) linker. Surface binding events were analyzed by electrochemical impedance spectroscopy (EIS) in which the formation of an antigen-antibody complex was quantified as a function of charge transfer resistance using a [Fe(CN)6](3-/4-) redox probe. The effectiveness of novel sym-triazine-derived aggregation modulators (TAE-1, TAE-2) to reduce the population of toxic oligomers was evaluated. Aβ fibril formation was validated by thioflavin T (ThT) fluorescence, whereas oligomer formation was investigated by MALDI. Antigen detection by EIS was further supported by immuno dot blot assays for oligomeric and fibrillar components. Docking simulations of the aggregation modulators TAE-1 and TAE-2 with Aβ(1-42) fibrils performed using Autodock Vina suggest a mechanism for the improved aggregation inhibition observed for TAE-2. The results demonstrate the utility and convenience of impedance immunosensing as an analytical tool for rapid and comprehensive evaluation of effective Aβ aggregation modulating agents.