Biology subjects

Stangherlin, A.

Publications and source records attributed to Stangherlin, A..

3 recordsLinked to original sources

bioRxiv2021

Differential effects of environmental and endogenous 24h rhythms within a deep-coverage spatiotemporal proteome

The cellular landscape of most eukaryotic cells changes dramatically over the course of a 24h day. Whilst the proteome responds directly to daily environmental cycles, it is also regulated by a cellular circadian clock that anticipates the differing demands of day and night. To quantify the relative contribution of diurnal versus circadian regulation, we mapped spatiotemporal proteome dynamics under 12h:12h light:dark cycles compared with constant light. Using Ostreococcus tauri, a prototypical eukaryotic cell, we achieved 85% coverage of the theoretical proteome which provided an unprecedented insight into the identity of proteins that drive and facilitate rhythmic cellular functions. Surprisingly, the overlap between diurnally- and circadian-regulated proteins was quite modest (11%). These proteins exhibited different phases of oscillation between the two conditions, consistent with an interaction between intrinsic and extrinsic regulatory factors. The relative amplitude of rhythmic protein abundance was much lower than would be expected from daily variations in transcript abundance. Transcript rhythmicity was poorly predictive of daily variation in abundance of the encoded protein. We observed coordination between the rhythmic regulation of organelle-encoded proteins with the nuclear-encoded proteins that are targeted to organelles. Rhythmic transmembrane proteins showed a remarkably different phase distribution compared with rhythmic soluble proteins, indicating the existence of a novel circadian regulatory process specific to the biogenesis and/or degradation of membrane proteins. Taken together, our observations argue that the daily spatiotemporal regulation of cellular proteome composition is not dictated solely by clock-regulated gene expression. Instead, it also involves extensive rhythmic post-transcriptional, translational, and post-translational regulation that is further modulated by environmental timing cues.

cell biology↗

bioRxiv2020

Compensatory ion transport buffers daily protein rhythms to regulate osmotic balance and cellular physiology

Between 6-20% of the cellular proteome is under circadian control to tune cell function with cycles of environmental change. For cell viability, and to maintain volume within narrow limits, the osmotic pressure exerted by changes in the soluble proteome must be compensated. The mechanisms and consequences underlying compensation are not known. Here, we show in cultured mammalian cells and in vivo that compensation requires electroneutral active transport of Na+, K+, and Cl- through differential activity of SLC12A family cotransporters. In cardiomyocytes ex vivo and in vivo, compensatory ion fluxes alter their electrical activity at different times of the day. Perturbation of soluble protein abundance has commensurate effects on ion composition and cellular function across the circadian cycle. Thus, circadian regulation of the proteome impacts ion homeostasis with substantial consequences for the physiology of electrically active cells such as cardiomyocytes.

cell biology↗

bioRxiv2020

CRYPTOCHROME suppresses the circadian proteome and promotes protein homeostasis

The daily organisation of most mammalian cellular functions is attributed to circadian regulation of clock-controlled protein expression, driven by daily cycles of CRYPTOCHROME-dependent transcriptional feedback repression. To test this, we compared the circadian proteome and phosphoproteome of wild type and CRY-deficient fibroblast cells. Strikingly, CRY-deficient cells showed a two-fold increase in circadian-regulated proteins, phosphopeptides, and K+ transport. This was accompanied by extensive remodelling of the cellular proteome overall, including reduced phosphatase and proteasome subunit expression. These adaptations rendered CRY-deficient cells more sensitive to stress, which may account for their reduced circadian robustness and contribute to the wide-ranging phenotypes of CRY-deficient mice. We suggest that CRY ultimately functions to suppress, rather than generate, daily rhythms in cellular protein abundance, thereby maintaining protein and osmotic homeostasis.

cell biology↗