Biology subjects

Willis, M. S.

Publications and source records attributed to Willis, M. S..

5 recordsLinked to original sources

bioRxiv2023

Low-Magnitude Mechanical Signals Combined with Zoledronic Acid Reduce Musculoskeletal Weakness and Adiposity in Estrogen-Deprived Mice

Combination treatment of Low-Intensity Vibration (LIV) with zoledronic acid (ZA) was hypothesized to preserve bone mass and muscle strength while reducing adipose tissue accrual associated with complete estrogen (E2)-deprivation in young and skeletally mature mice. Complete E2-deprivation (surgical-ovariectomy (OVX) and daily injection of aromatase inhibitor (AI) letrozole) were performed on 8-week-old C57BL/6 female mice for 4 weeks following commencement of LIV administration or control (no LIV), for 28 weeks. Additionally, 16-week-old C57BL/6 female E2-deprived mice were administered {+/-}LIV twice daily and supplemented with {+/-}ZA (2.5 ng/kg/week). By week 28, lean tissue mass quantified by dual-energy X-ray absorptiometry was increased in younger OVX/AI+LIV(y) mice, with increased myofiber cross-sectional area of quadratus femorii. Grip strength was greater in OVX/AI+LIV(y) mice than OVX/AI(y) mice. Fat mass remained lower in OVX/AI+LIV(y) mice throughout the experiment compared with OVX/AI(y) mice. OVX/AI+LIV(y) mice exhibited increased glucose tolerance and reduced leptin and free fatty acids than OVX/AI(y) mice. Trabecular bone volume fraction and connectivity density increased in the vertebrae of OVX/AI+LIV(y) mice compared to OVX/AI(y) mice; however, this effect was attenuated in the older cohort of E2-deprived mice, specifically in OVX/AI+ZA mice, requiring combined LIV with ZA to increase trabecular bone volume and strength. Similar improvements in cortical bone thickness and cross-sectional area of the femoral mid-diaphysis were observed in OVX/AI+LIV+ZA mice, resulting in greater fracture resistance. Our findings demonstrate that the combination of mechanical signals in the form of LIV and anti-resorptive therapy via ZA improve vertebral trabecular bone and femoral cortical bone, increase lean mass, and reduce adiposity in mice undergoing complete E2-deprivation. One Sentence Summary: Low-magnitude mechanical signals with zoledronic acid suppressed bone and muscle loss and adiposity in mice undergoing complete estrogen deprivation. Translational RelevancePostmenopausal patients with estrogen receptor-positive breast cancer treated with aromatase inhibitors to reduce tumor progression experience deleterious effects to bone and muscle subsequently develop muscle weakness, bone fragility, and adipose tissue accrual. Bisphosphonates (i.e., zoledronic acid) prescribed to inhibit osteoclast-mediated bone resorption are effective in preventing bone loss but may not address the non-skeletal effects of muscle weakness and fat accumulation that contribute to patient morbidity. Mechanical signals, typically delivered to the musculoskeletal system during exercise/physical activity, are integral for maintaining bone and muscle health; however, patients undergoing treatments for breast cancer often experience decreased physical activity which further accelerates musculoskeletal degeneration. Low-magnitude mechanical signals, in the form of low-intensity vibrations, generate dynamic loading forces similar to those derived from skeletal muscle contractility. As an adjuvant to existing treatment strategies, low-intensity vibrations may preserve or rescue diminished bone and muscle degraded by breast cancer treatment.

cancer biology↗

bioRxiv2020

BAG3-dependent autophagy maintains sarcomere function in cardiomyocytes

The association between reduced myofilament force-generating capacity (Fmax) and heart failure (HF) is clear, however the underlying molecular mechanisms are poorly understood. Here, we show the Fmax decrease arises from impaired BAG3-mediated sarcomere turnover. Myofilament BAG3 decreased in human HF and predicted the extent of Fmax decrease. This relationship was confirmed using BAG3+/- mice, which had reduced Fmax and increased myofilament ubiquitination, suggesting impaired protein turnover. We show cardiac BAG3 operates via the chaperone-assisted selective autophagy complex (CASA), conserved from skeletal muscle, and confirm sarcomeric CASA localization is BAG3/proteotoxic stress-dependent. To determine if increasing BAG3 expression in HF would restore sarcomere proteostasis/Fmax, HF mice were treated with AAV9/BAG3. Gene therapy fully restored Fmax after four weeks and decreased ubiquitination. Using mass spectrometry, we identified several sarcomere proteins with increased ubiquitination in HF and four that decreased with AAV9/BAG3. Our findings indicate BAG3-mediated sarcomere turnover is required for myofilament functional maintenance.

physiology↗

bioRxiv2020

Cardiomyocyte-specific ACSL1 Deficiency Prevents Cardiac Lipotoxicity and Alleviates Heart Dysfunction in the ob/ob Model of Obesity

Cardiac lipotoxicity is associated with structural remodeling and functional changes that are features of obesity-related cardiomyopathy. Both high fat diet and the ob/ob mutation lead to increased fatty acid (FA) uptake, elevated triacylglycerol (TAG) content, hypertrophy, and systolic and diastolic dysfunction in murine hearts. Cardiomyocyte-specific long-chain acyl-CoA synthetase 1 (ACSL1) deficiency (Acsl1H-/-) results in a 90% reduction in FA activation, suggesting that Acsl1 ablation might alleviate obesity-associated myocardial dysfunction. Double knockout ob-Acsl1H-/- and ob-Acsl1flox/flox control mice were treated with tamoxifen at 20 weeks of age; heart function, TAG content, and relevant gene expression were assessed immediately before and 2 and 5 weeks after treatment. Heart weights initially increased in lean and obese Acsl1H-/- mice, but normalized in ob-Acsl1H-/- mice by 5 weeks. Ventricular TAG content was decreased by 51% and 61% in ob-Acsl1H-/- mice 2 and 5 weeks after Acsl1 knockout induction, respectively. Moreover, ACSL1 knockout resulted in increased survival of ob/ob mice, suggesting that lack of ACSL1 protected obese hearts subjected to stress. Our results indicate that partial knockdown of cardiac ACSL1 is sufficient to reverse cardiac TAG accumulation and to ameliorate heart dysfunction even in the context of established obesity-related cardiomyopathy.

physiology↗

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↗

bioRxiv2017

Loss of CHIP Expression Perturbs Glucose Homeostasis and Leads to Type II Diabetes through Defects in Microtubule Polymerization and Glucose Transporter Localization

Recent evidence has implicated CHIP (carboxyl terminus of Hsc/Hsp70-interacting protein), a co-chaperone and ubiquitin ligase, in the functional support of several metabolism-related proteins, including AMPK and SirT6. In addition to previously reported aging and stress intolerance phenotypes, we find that CHIP -/- mice also demonstrate a Type II diabetes-like phenotype, including poor glucose tolerance, decreased sensitivity to insulin, and decreased insulin-stimulated glucose uptake in isolated skeletal muscle, characteristic of insulin resistance. In CHIP-deficient cells, glucose stimulation fails to induce translocation of Glut4 to the plasma membrane. This impairment in Glut4 translocation in CHIP-deficient cells is accompanied by decreased tubulin polymerization associated with decreased phosphorylation of stathmin, a microtubule-associated protein required for polymerization-dependent protein trafficking within the cell. Together, these data describe a novel role for CHIP in regulating microtubule polymerization that assists in glucose transporter translocation, promoting whole-body glucose homeostasis and sensitivity to insulin.

physiology↗