Biology subjects

Parisi, B.

Publications and source records attributed to Parisi, B..

4 recordsLinked to original sources

bioRxiv2026

Regulation of de- and reciliation by KRAS during muscle cell differentiation

The primary cilium has been implicated in multiple developmental processes, such as cell migration and asymmetric cell division of stem- and progenitor cells. While most in vitro model systems examine ciliogenesis induced by serum starvation, it is not fully understood how de-and re-ciliation are regulated in proliferating stem- and progenitor cells. Here we employ the hierarchically organized C2C12 skeletal muscle cell line to examine how K-Ras4B participates in de- and re-ciliation processes of ciliated stem- and progenitor cells. We show that MAPK-pathway activation supports ciliogenesis through phosphorylation of centrosomal protein CEP55, which can then no longer stabilize the master regulator of de-ciliation Aurora kinase A. K-Ras4B localizes to the primary cilium aided by the ciliary trafficking chaperone PDE6D, which promotes ciliation. In line with this, depletion of components of the PDE6D machinery, RPGR and RPGRIP1L, decreases ciliation. Activation of the ciliary AMPK-PKG2-pathway increases S181-phosphorylation of K-Ras4B, which negatively regulates its binding to PDE6D, its ciliary abundance and promotes differentiation. Our work integrates a major mediator of mitogenic signaling into the regulation of ciliogenesis of proliferating muscle stem- and progenitor cells.

cell biology↗

bioRxiv2026

K-Ras controls asymmetric cell divisions from the primary cilium

The Ras-MAPK pathway drives central cellular processes, including cell proliferation and differentiation. How exactly Ras controls differentiation is however not understood. Supported by mathematical modelling and single-cell RNA sequencing we show that K-Ras4B sustains ciliation during differentiation thus restricting commitment of skeletal muscle stem and progenitor cells during asymmetric cell divisions. Modulation of K-Ras4B abundance or expression of oncogenic K-Ras4B-G12C perturb normal differentiation. K-Ras4B, but not N-Ras and H-Ras, localizes to the primary cilium and its abundance there depends on the ciliary trafficking chaperone PDE6D. The presence of B-Raf and active MEK at the base of and active ERK inside the cilium suggests that K-Ras4B is active there. Conditions that localize a K-Ras4B mutant only to the cilium are sufficient to sustain ciliation and normal differentiation. Finally, in vivo modulation of K-Ras4B activity during zebrafish embryogenesis perturbs ciliation-dependent heart-looping. Our results thus imply a novel fundamental role of K-Ras4B in controlling ciliation and differentiation and suggest an explanation for the phenotypic similarities between RASopathies and ciliopathies.

cell biology↗

bioRxiv2026

Strong sustained type I IFN signaling acts cell intrinsically to impair IFNγ responses and cause tuberculosis susceptibility

Mycobacterium tuberculosis (Mtb) causes over one million deaths annually, but most infected individuals never exhibit symptoms. Type I interferons (IFNs) have emerged as a major factor driving susceptibility to Mtb, but how type I IFNs impair immunity to Mtb is a key unresolved question. Here we show that an early effect of type I IFN during Mtb infection is the cell-intrinsic impairment of IFN{gamma} signaling. IFN{gamma} signaling was selectively impaired in the subset of infected macrophages experiencing high and sustained levels of type I IFN signaling. Genetic elimination of RESIST, a recently described positive regulator of type I IFN production, specifically eliminated the high and sustained type I IFN response, fully restored IFN{gamma} signaling, and rescued susceptibility to Mtb without affecting basal type I IFN responses. Our results demonstrate that strong and sustained type I IFN responses specifically and cell intrinsically impair responsiveness to IFN{gamma} to cause susceptibility to Mtb.

immunology↗

bioRxiv2023

RAS isoform specific activities are disrupted by disease associated mutations during cell differentiation

The Ras-MAPK pathway is aberrantly regulated in cancer and developmental diseases called RASopathies. While typically the impact of Ras on the proliferation of various cancer cell lines is assessed, it is poorly established how Ras affects cellular differentiation. Here we implement the C2C12 myoblast cell line to systematically study the effect of Ras mutants and Ras-pathway drugs on differentiation. We first provide evidence that a minor pool of Pax7+ progenitors replenishes a major pool of transit amplifying cells that are ready to differentiate. Our data indicate that Ras isoforms have distinct roles in the differentiating culture, where K-Ras is more important than N-Ras to maintain the progenitor pool and H-Ras is significant for terminal differentiation. This assay could therefore provide significant new insights into Ras biology and Ras-driven diseases. In line with this, we found that all oncogenic Ras mutants block terminal differentiation of transit amplifying cells. Notably, while RASopathy K-Ras variants that are also NF1-GAP resistant also block differentiation, albeit less than their oncogenic counterparts. Profiling of targeted Ras-pathway drugs on oncogenic Ras mutants revealed their distinct abilities to restore normal differentiation as compared to triggering cell death. In particular, the MEK-inhibitor trametinib could broadly restore differentiation, while the mTOR-inhibitor rapamycin broadly suppressed differentiation. We expect that this quantitative assessment of the impact of Ras-pathway mutants and drugs on cellular differentiation has great potential to complement cancer cell proliferation data.

cell biology↗