Biology subjects

Sanchez-Hodge, R.

Publications and source records attributed to Sanchez-Hodge, R..

3 recordsLinked to original sources

bioRxiv2025

Domain-specific decoupling of co-chaperone and ligase functions in STUB1 underlies biochemical and clinical heterogeneity in SCA48

AO_SCPLOWBSTRACTC_SCPLOWThe carboxyl terminus of HSC70-interacting protein (CHIP, encoded by STUB1) integrates co-chaperone and E3 ubiquitin ligase activities to maintain proteostasis. Heterozygous STUB1 mutations cause the dominant cerebellar ataxia SCA48 through incompletely understood mechanisms. We characterized 13 SCA48-associated variants in the TPR and U-box domains using recombinant protein and cellular assays. TPR mutations retained intrinsic ligase activity but lost HSC70 binding, substrate ubiquitination efficiency, and protein stability. Conversely, U-box mutations abolished ligase function, induced aberrant high-molecular-weight oligomerization, and frequently elevated steady-state CHIP levels while only partially impairing co-chaperone activity. Many variants exhibited temperature-sensitive defects and stress-induced nuclear mislocalization. Principal component analysis revealed robust domain-specific biochemical clustering. RNA-seq following STUB1 knockdown demonstrated preserved HSF1-dependent transactivation but a loss of CHIP-dependent amplification of ubiquitination, chaperone, and transcriptional pathways under heat stress. Meta-analysis of 87 SCA48 patients linked TPR-like biochemical profiles to upper motor neuron involvement and U-box profiles to prominent dysarthria. Collectively, SCA48 mutations decouple CHIPs dual functions in a domain-dependent manner, exerting dominant-negative or gain-of-toxic effects that drive the observed clinical heterogeneity. These findings establish a direct biochemical-clinical correlation in SCA48 and provide a framework for domain-targeted therapeutic strategies exploiting residual ligase or chaperone activity.

neuroscience↗

bioRxiv2019

Evaluating the efficacy of enzalutamide and the development of resistance in a preclinical mouse model of type-I endometrial carcinoma

Androgen Receptor (AR) signaling is a critical driver of hormone-dependent prostate cancer and has also been proposed to have biological activity in female hormone-dependent cancers, including type I endometrial carcinoma (EMC). In this study, we evaluated the preclinical efficacy of a third-generation AR antagonist, enzalutamide, in a genetic mouse model of EMC, Sprr2f-Cre;Ptenfl/fl. In this model, ablation of Pten in the uterine epithelium leads to localized and distant malignant disease as observed in human EMC. We hypothesized that administering enzalutamide through the diet would temporarily decrease the incidence of invasive and metastatic carcinoma, while prolonged administration would result in development of resistance and loss of efficacy. Short-term treatment with enzalutamide reduced overall tumor burden through increased apoptosis but failed to prevent progression of invasive and metastatic disease. These results suggest that AR signaling may have biphasic, oncogenic and tumor suppressive roles in EMC that are dependent on disease stage. Enzalutamide treatment increased Progesterone Receptor (PR) expression within both stromal and tumor cell compartments. Prolonged administration of enzalutamide decreased apoptosis, increased tumor burden and resulted in the clonal expansion of tumor cells expressing high levels of p53 protein, suggestive of acquired Trp53 mutations. In conclusion, we show that enzalutamide induces apoptosis in EMC but has limited efficacy overall as a single agent. Induction of PR, a negative regulator of endometrial proliferation, suggests that adding progestin therapy to enzalutamide administration may further decrease tumor burden and result in a prolonged response.

cancer biology↗

bioRxiv2018

Disrupted structure and aberrant function of CHIP mediates the loss of motor and cognitive function in preclinical models of cerebellar CHIPopathy

CHIP (carboxyl terminus of heat shock 70-interacting protein) has long been recognized as an active member of the cellular protein quality control system given the ability of CHIP to function as both a co-chaperone and ubiquitin ligase. Mutations in CHIP are the driver of spinocerebellar autosomal recessive 16 (SCAR16), or cerebellar CHIPopathy, as we initially discovered this disease was caused by a loss of CHIP ubiquitin ligase function. The initial mutation describing SCAR16 was a missense mutation in the ubiquitin ligase domain of CHIP (p.T246M). Using multiple biophysical and cellular approaches, we demonstrate that T246M mutation results in structural disorganization and misfolding of the CHIP U-box domain, promoting oligomerization, and increased proteasome-dependent turnover. CHIP-T246M has no ligase activity, but maintains interactions with chaperones and alters the co-chaperone function of CHIP. To establish preclinical models of SCAR16, we engineered T246M at the endogenous locus in both mice and rats. Animals homozygous for T246M had both cognitive and motor cerebellar dysfunction distinct from those observed in the CHIP null animal model, as well as deficits in learning and memory, reflective of the cognitive deficits reported in SCAR16 patients. We conclude that the T246M mutation is not equivalent to the total loss of CHIP, supporting the concept that disease-causing CHIP mutations have different biophysical and functional repercussions on CHIP function that may directly correlate to the spectrum of clinical phenotypes observed in SCAR16 patients. Our findings both further expand our basic understanding of CHIP biology and provide meaningful mechanistic insight underlying the molecular drivers of SCAR16 disease pathology, which may be used to inform the development of novel therapeutics for this devastating disease.

animal behavior and cognition↗