👤 Joao A Paulo

HNF1A-MODY, the most prevalent form of monogenic diabetes, displays incomplete penetrance, indicating the involvement of other environmental and genetic factors in the disease etiology. Currently, it is largely unknown what the influence of environmental factors, such as toxins or diet, is on HNF1A-MODY onset and progression. Here we address this issue by exploring the impact of diet on islet and insulin-secreting beta-cells in the context of HNF1A mutation. Transgenic mice allowing the specific Hnf1a mutation in insulin-secreting beta-cells were exposed to four distinct dietary regimens including combinations of high-fat diet and caloric restriction. In vitro stem cell islets bearing the HNF1A Hnf1a-deficient beta-cells exhibited high sensitivity to dietary cues. Exposure to a high-fat diet exacerbated the glucose regulation defects, while caloric restriction significantly improved blood glucose levels in vivo, without perturbing islet architecture. The high-throughput methods identified changes in the Hnf1a-deficient beta-cells proteome landscape, involving conserved critical regulators of metabolic and growth processes, such as the Carbohydrate Response Element Binding Protein (Chrebp/Mlxipl) and ATP citrate lyase (Acly) among others. This study hallmarks the important impact of diet on Hnf1a-deficient beta-cells, stemming new therapeutic perspectives, such as future diet management approaches. Show less

WWP2 is a HECT E3 ligase that targets protein Lys residues for ubiquitination and is comprised of an N-terminal C2 domain, four central WW domains, and a C-terminal catalytic HECT domain. The peptide segment between the middle WW domains, the 2,3-linker, is known to autoinhibit the catalytic domain, and this autoinhibition can be relieved by phosphorylation at Tyr369. Several protein substrates of WWP2 have been identified, including the tumor suppressor lipid phosphatase PTEN, but the full substrate landscape and biological functions of WWP2 remain to be elucidated. Here, we used protein microarray technology and the activated enzyme phosphomimetic mutant WWP2 Show less

Selective autophagy and macroautophagy sequester specific organelles/substrates or bulk cytoplasm, respectively, inside autophagosomes as cargo for delivery to lysosomes. The mammalian ATG8 orthologues (MAP1LC3A/B/C and GABARAP/L1/L2) are ubiquitin (UB)-like proteins conjugated to the autophagosome membrane and are thought to facilitate cargo receptor recruitment, vesicle maturation, and lysosomal fusion. To elucidate the molecular functions of the ATG8 proteins, we engineered cells lacking genes for each subfamily as well as all six mammalian ATG8s. Loss of GABARAPs alone attenuates autophagic flux basally and in response to macroautophagic or selective autophagic stimuli, including parkin-dependent mitophagy, and cells lacking all ATG8 proteins accumulate cytoplasmic UB aggregates, which are resolved following ectopic expression of individual GABARAPs. Autophagosomes from cells lacking GABARAPs had reduced lysosomal content by quantitative proteomics, consistent with fusion defects, but accumulated regulators of late endosome (LE)/autophagosome maturation. Through interaction proteomics of proteins accumulating in GABARAP/L1/L2-deficient cells, we identified C18orf8/RMC1 as a new subunit of the CCZ1-MON1 RAB7 guanine exchange factor (GEF) that positively regulates RAB7 recruitment to LE/autophagosomes. This work defines unique roles for GABARAP and LC3 subfamilies in macroautophagy and selective autophagy and demonstrates how analysis of autophagic machinery in the absence of flux can identify new regulatory circuits. Show less