van Deursen, J. | bioRxiv Science

bioRxiv2022

HD-PTP/PTPN23 hypomorphic mice display lipodystrophy

Endosomal Sorting Complexes Required for Transport (ESCRTs) drive reverse topology membrane remodeling events including the formation of intralumenal vesicles within multivesicular bodies, the budding of retroviruses from the plasma membrane, and the scission of the cytokinetic bridge. It has been difficult to study the physiological relevance of this machinery in mammals because many contributing components are essential for viability. To bypass this problem we used combinations of knockout (-), hypomorphic (H) and wildtype (+) alleles to generate a series of mice with a gradual reduction of HD-PTP (product of PTPN23), an ESCRT-associated protein known to cause embryonic lethality when fully depleted. Whereas PTPN23-/H mice died shortly after birth, PTPN23H/H mice developed into adulthood but had reduced size, lipodystrophy, and shortened lifespan. Analysis of 14-day inguinal adipose tissue indicated reduced expression of adipogenesis markers, and PTPN23 knockout preadipocytes similarly display reduced adipogenesis in vitro. Defects in insulin-stimulated signaling were apparent in differentiated PTPN23 knockout adipocytes and PTPN23H/H inguinal adipose tissue in vitro, correlating with reduced levels of insulin signaling hallmarks observed in adult PTPN23H/H inguinal adipose tissue in vivo. Whereas the ESCRT machinery have been suggested to downregulate signaling, these results indicate that HD-PTP promotes insulin-induced signaling in, as well as differentiation of, inguinal adipose tissue. These results revealed unexpected roles for HD-PTP in promoting fat accumulation in mammalian cells through supporting insulin signaling, adipogenesis, and lipid droplet formation.

cell biology↗

bioRxiv2021

Deletion of Serf2 shifts amyloid conformation in an Aβ amyloid mouse model

In age-related neurodegenerative disease, like Alzheimers and Parkinsons disease, disease-specific proteins become aggregation-prone and form amyloid-like deposits. Depletion of SERF proteins ameliorates this toxic process in worm- and human cell models for disease. Whether SERF modifies amyloid pathology in mammalian brain, however, has remained unknown. Here, we generated SERF2 brain-specific knockout mice which, unlike full body knockout mice, were viable, and showed no major behavioral and cognitive abnormalities. We combined these knockout mice with the APPPS1 mouse model for human amyloid beta aggregation. Using structure-specific amyloid dyes, previously used to distinguish amyloid polymorphisms in human brain, we show that knockout of SERF2 alters the structure of amyloid fibrils and deposits. Moreover, scanning transmission electron microscopy revealed thicker, shorter and more densely packed amyloid in absence of SERF2. Altogether, our data reveal pleiotropic functions of SERF in development and aging and support a function as a modifier of amyloid aggregation in mammalian brain. Our results indicate that single cellular factors like SERF can determine the structural outcome of amyloid aggregation, offering possibilities for polymorphism-based disease interventions.

molecular biology↗