Biology subjects

Rotman, S.

Publications and source records attributed to Rotman, S..

4 recordsLinked to original sources

bioRxiv2026

VAPB and its binding partner AKAP11 promote lipid droplet degradation

The endoplasmic reticulum (ER) is the master regulator of various cellular processes. To achieve its diverse functions, the ER interacts with other organelles at membrane contact sites, regions where organelles are brought into proximity. Most ER membrane contact sites are facilitated by the ER-resident VAP proteins. To address the role of VAP proteins in regulating cellular lipid homeostasis, we performed a targeted lipidomic screen after silencing individual VAPs. The loss of VAPB increases cellular levels of neutral lipids stored in lipid droplets (LDs). The increase in neutral lipids is reflected in the size, number and motility of LDs, and is due to the impaired degradation of these organelles. VAPB requires its contact site forming ability to regulate LDs, prompting the identification of protein kinase A (PKA) anchor AKAP11 as a VAPB interaction partner in regulating LD degradation and dynamics. Collectively, our findings identify a role for the ER-resident VAPB-AKAP11 interaction and PKA activity in regulating LD homeostasis. SummaryThe ER-resident membrane contact site protein VAPB and its interaction partner AKAP11 regulate lipid droplet size and motility by mediating neutral lipid degradation. VAPB requires its ability to form membrane contact sites and interact with AKAP11, protein kinase A anchor protein, for mediating lipid droplet homeostasis. This paper uncovers a role for VAPB-AKAP11-PKA axis in regulating the homeostasis of lipid droplets.

cell biology↗

bioRxiv2025

Identification of RNF114 as ADPr-Ub reader through non-hydrolysable ubiquitinated ADP-ribose

Crosstalk between the post-translational modification processes ubiquitination and ADP-ribosylation occurs in DNA-damage and immune-responses, in addition the physical linkage of ADP-ribose and ubiquitin is found during bacterial infection. Here, we study the ubiquitination of ADP-ribose mediated by human Deltex E3 ligases and the subsequent fate of the formed hybrid post-translational modification. We prepare a non-hydrolysable ADPr-Ub probe that we employ in a chemoproteomics approach and identify RNF114 as an interacting protein. Using biophysical and biochemical experiments, we validate that RNF114 preferentially interacts with ubiquitinated ADP-ribose over non-modified ubiquitin. Subsequently, RNF114 can elongate the ubiquitinated ADP-ribose with a K11-linked ubiquitin chain. Using domain deletion analysis, we pinpoint the tandem zinc fingers and ubiquitin interacting motif (ZnF2+ZnF3+UIM) domains of RNF114 to be crucial for recognising ubiquitinated ADP-ribose. Moreover, these domains are essential for the recruitment of RNF114 to the sites of laser-induced DNA damage.

molecular biology↗

bioRxiv2025

Multi-omics reveals global signaling rewiring and identifies Activin A-induced dysregulation of FOS/Activator Protein 1 as a novel target in Fibrodysplasia ossificans progressiva

BackgroundFibrodysplasia ossificans progressiva (FOP) is caused by an activating mutation (p.R206H) in the type I BMP receptor ALK2, leading to heterotopic ossification (HO) in soft connective tissues. While aberrant Activin A-induced SMAD signaling is central in FOP pathogenesis, global signaling alterations remain poorly understood. MethodsWe performed phosphoproteomics, transcriptomics and biochemical analyses in mesenchymal cells (MSCs) overexpressing wild-type ALK2WT or mutant ALK2R206H receptors and in induced-MSCs derived from FOP patient iPSCs. Findings were validated in vivo using FOP-like mouse models and in vitro via pharmacological interventions. ResultsMulti-omics analyses revealed previously unrecognized signaling networks in ALK2R206H cells, including enhanced MAPK, mTOR, RUNX2 and RHO-mediated mechanotransduction pathways. Notably, we identified dysregulated Activator Protein-1 (AP-1) expression and function as a novel contributor to FOP. AP-1 factors were highly enriched in HO lesions in FOP-like animals. Pharmacological inhibition of AP-1 significantly reduced osteochondrogenic differentiation in vitro. ConclusionThis study highlights global signaling dysregulation in FOP and identifies AP-1 as a critical driver and potential therapeutic target for FOP.

molecular biology↗

bioRxiv2019

Leveraging biobank-scale rare and common variant analyses to identify ASPHD1 as the main driver of reproductive traits in the 16p11.2 locus

Whereas genome-wide association studies (GWAS) allowed identifying thousands of associations between variants and traits, their success rate in pinpointing causal genes has been disproportionately low. Here, we integrate biobank-scale phenotype data from carriers of a rare copy-number variant (CNV), Mendelian randomization and animal modeling to identify causative genes in a GWAS locus for age at menarche (AaM). We show that the dosage of the 16p11.2 BP4-BP5 interval is correlated positively with AaM in the UK and Estonian biobanks and 16p11.2 clinical cohorts, with a directionally consistent trend for pubertal onset in males. These correlations parallel an increase in reproductive tract disorders in both sexes. In support of these observations, 16p11.2 mouse models display perturbed pubertal onset and structurally altered reproductive organs that track with CNV dose. Further, we report a negative correlation between the 16p11.2 dosage and relative hypothalamic volume in both humans and mice, intimating a perturbation in the gonadotropin-releasing hormone (GnRH) axis. Two independent lines of evidence identified candidate causal genes for AaM; Mendelian randomization and agnostic dosage modulation of each 16p11.2 gene in zebrafish gnrh3:egfp models. ASPHD1, expressed predominantly in brain and pituitary gland, emerged as a major phenotype driver; and it is subject to modulation by KCTD13 to exacerbate GnRH neuron phenotype. Together, our data highlight the power of an interdisciplinary approach to elucidate disease etiologies underlying complex traits.

genomics↗