Bantis, L. E. | Search bioRxiv

bioRxiv2020

"Multiplex" rheostat positions cluster around allosterically critical regions of the lactose repressor protein

Amino acid variation at "rheostat" positions provides opportunity to modulate various aspects of protein function - such as binding affinity or allosteric coupling - across a wide range. Previously a subclass of "multiplex" rheostat positions was identified at which substitutions simultaneously modulated more than one functional parameter. Using the Miller laboratorys dataset of [~]4000 variants of lactose repressor protein (LacI), we compared the structural properties of multiplex rheostat positions with (i) "single" rheostat positions that modulate only one functional parameter, (ii) "toggle" positions that follow textbook substitution rules, and (iii) "neutral" positions that tolerate any substitution without changing function. The combined rheostat classes comprised >40% of LacI positions, more than either toggle or neutral positions. Single rheostat positions were broadly distributed over the structure. Multiplex rheostat positions structurally overlapped with positions involved in allosteric regulation. When their phenotypic outcomes were interpreted within a thermodynamic framework, functional changes at multiplex positions were uncorrelated. This suggests that substitutions lead to complex changes in the underlying molecular biophysics. Bivariable and multivariable analyses of evolutionary signals within multiple sequence alignments could not differentiate single and multiplex rheostat positions. Phylogenetic analyses - such as ConSurf - could distinguish rheostats from toggle and neutral positions. Multivariable analyses could also identify a subset of neutral positions with high probability. Taken together, these results suggest that detailed understanding of the underlying molecular biophysics, likely including protein dynamics, will be required to discriminate single and multiplex rheostat positions from each other and to predict substitution outcomes at these sites.

biochemistry↗

bioRxiv2020

A high fat anti-inflammatory diet improves widespread allodynia despite worsening metabolic outcomes in adult mice exposed to neonatal maternal separation

Inflammation plays a key role in the progression and maintenance of chronic pain, which impacts the lives of millions of Americans. Despite growing evidence that chronic pain can be improved by treating underlying inflammation, successful treatments are lacking and pharmaceutical interventions are limited due to drug side effects. Here we are testing whether an anti-inflammatory diet (AID) containing a combination of key anti-inflammatory compounds, at clinically relevant doses, improves pain-like behaviors in a preclinical model of chronic widespread hypersensitivity induced by neonatal maternal separation (NMS). Our results demonstrate a benefit of the AID on pain-like behaviors, despite the diet being high in fat, which led to increased caloric intake, adiposity, and weight gain. The AID specifically increased measures of metabolic syndrome and inflammation in female mice, compared to an isocaloric, macronutrient-matched diet lacking the anti-inflammatory compounds. Male mice, especially those exposed to NMS, were equally susceptible to both diets worsening metabolic measures. This work highlights important sexual dimorphic outcomes related to early life stress exposure and dietary interventions, as well as a potential disconnect between improvements in pain-like behaviors and metabolic measures.

physiology↗