Haploinsufficiency of the E3 Ubiquitin Ligase C-Terminus of Heat Shock Cognate 70 Interacting Protein (CHIP) Produces Specific Behavioral Impairments

Abstract

The multifunctional E3 ubiquitin ligase CHIP is an essential interacting partner of HSP70, which together promote the proteasomal degradation of client proteins. Acute CHIP overexpression provides neuroprotection against neurotoxic mitochondrial stress, glucocorticoids, and accumulation of toxic amyloid fragments, as well as genetic mutations in other E3 ligases, which have been shown to result in familial Parkinson's disease. These studies have created a great deal of interest in understanding CHIP activity, expression and modulation. While CHIP knockout mice have the potential to provide essential insights into the molecular control of cell fate and survival, the animals have been difficult to characterize in vivo due to severe phenotypic and behavioral dysfunction, which have thus far been poorly characterized. Therefore, in the present study we conducted a battery of neurobehavioral and physiological assays of adult CHIP heterozygotic (HET) mutant mice to provide a better understanding of the functional consequence of CHIP deficiency. We found that CHIP HET mice had normal body and brain weight, body temperature, muscle tone and breathing patterns, but do have a significant elevation in baseline heart rate. Meanwhile basic behavioral screens of sensory, motor, emotional and cognitive functions were normative. We observed no alterations in performance in the elevated plus maze, light-dark preference and tail suspension assays, or two simple cognitive tasks: novel object recognition and spontaneous alternation in a Y maze. Significant deficits were found, however, when CHIP HET mice performed wire hang, inverted screen, wire maneuver, and open field tasks. Taken together, our data indicate a clear subset of behaviors that are altered at baseline in CHIP deficient animals, which will further guide whole animal studies of the effects of CHIP dysregulation on cardiac function, brain circuitry and function, and responsiveness to environmental and cellular stress.

CHIP Is an Essential Determinant of Neuronal Mitochondrial Stress Signaling

“…The role of mitophagy has come under particular scrutiny lately as an increasing number of proteins have linked neurodegeneration with aberrant mitophagy (4, 5, 52, 59). Acute overexpression of CHIP is neuroprotective against a number of acute and chronic stressors, and we recently reported that CHIP KO mice are uniquely impaired by the loss of this ligase, which dramatically decreases life span (8), impairs motor skills (29,38), and alters anxiety responses (29). We show in the current work that these mice also present with atypical CNS protein oxidation and lipid peroxidation, decreased antioxidant responses, and impaired bioenergetic status at baseline.…”

“…We recently reported that C-terminus of HSC70-interacting protein (CHIP) haploinsufficiency results in mild behavioral impairments and profound changes in motor function in young animals (29). These data are particularly striking given that deletion of Parkin has a benign phenotype (43), whereas loss of CHIP is catastrophic early in life, resulting in the death of *30% of animals by postnatal day (PND)40 (8,38).…”

Subtle biobehavioral effects produced by paternal cocaine exposure

“…Sessions were recorded by a ceiling‐mounted video camera connected to a computer using video acquisition and analysis software (ANY‐maze, Stoelting, Wood Dale, IL). Data analyzed included the amount of time in andnumber of entries into each zone of the maze (Carpenter et al, 2012; McLaughlin et al,2012).…”

“…Locomotor activity in a novel open field was measured using commercial open field activity chambers (Med Associates, 27 cm × 27 cm × 20.5 cm) that were contained within light‐ and air‐controlled environmental chambers (Med Associates, 64 cm × 45 cm × 42 cm). Location and movement were detected by the interruption of infrared beams by the body of the mouse (16 photocells in each horizontal direction as well as 16 photocells elevated 4 cm to measure rearing) and were measured by the Med Associates Activity Monitor program (McLaughlin et al,2012; Stanwood and Levitt,2007b). Activity was measured for a 60‐min session.…”

Simple shelter-style environmental enrichment alters behavior in mice

“…Behavioral despair was assessed in the forced swim test using plastic cylinders (14.5 cm in diameter, 21 cm in height) filled approximately ¾ full with room temperature water [34,36].…”