The nutrient sensor OGT regulates Hipk stability and tumorigenic-like activities inDrosophila

Abstract

Environmental cues such as nutrients alter cellular behaviors by acting on a wide array of molecular sensors inside cells. Of emerging interest is the link observed between effects of dietary sugars on cancer proliferation. Here, we identify the requirements of hexosamine biosynthetic pathway (HBP) and O-GlcNAc transferase (OGT) for Drosophila homeodomain-interacting protein kinase (Hipk)-induced growth abnormalities in response to a high sugar diet. On a normal diet, OGT is both necessary and sufficient for inducing Hipk-mediated tumor-like growth. We further show that OGT maintains Hipk protein stability by blocking its proteasomal degradation and that Hipk is O-GlcNAcylated by OGT. In mammalian cells, human HIPK2 proteins accumulate posttranscriptionally upon OGT overexpression. Mass spectrometry analyses reveal that HIPK2 is at least O-GlcNAc modified at S852, T1009, and S1147 residues. Mutations of these residues reduce HIPK2 O-GlcNAcylation and stability. Together, our data demonstrate a conserved role of OGT in positively regulating the protein stability of HIPKs (fly Hipk and human HIPK2), which likely permits the nutritional responsiveness of HIPKs.

Hyperpolarized mitochondria accumulate in Drosophila Hipk-overexpressing cells to drive tumor-like growth

“…mito-GFP, a mitochondrially targeted GFP) were co-expressed to mark the transgene-expressing cells. As previously reported ( Blaquiere et al, 2018 ; Wong et al, 2019 , 2020 ), in contrast to control wing discs ( dpp>mito-GFP ) ( Fig. 1 A), hipk- overexpressing discs ( dpp>mito-GFP+hipk ) manifested marked expansion of the GFP-positive area (the transgene-expressing Dpp domain) and distorted tissue morphology (as revealed by DNA staining) ( Fig.…”

Metabolic reprogramming in cancer: mechanistic insights from Drosophila

“…A growing number of cancer-related proteins are O- GlcNAc modified, for instance, MYC ( Chou et al, 1995a , b ) and the core components of Hippo signaling, including YAP ( Peng et al, 2017 ; Zhang et al, 2017 ) and LATS2 ( Kim et al, 2020 ). OGT also O- GlcNAcylates the fly proto-oncogene Hipk and human HIPK2 and promotes their stability ( Wong et al, 2020b ). Feeding Hipk -overexpressing larvae a high-sucrose diet potentiates the tumorigenic activities of Hipk through the HBP/OGT axis ( Fig.…”

Functional characterization of human Homeodomain-interacting protein kinases (HIPKs) inDrosophila melanogasterreveal both conserved functions and differential induction of HOX gene expression

“…Expressing UAS-dhipk at high levels using dpp-Gal4 at 29°C causes malformed adult legs [30]. When expressing UAS-hHIPKs with dpp-Gal4 , we found that UAS-hHIPK3 caused similarly malformed legs, while UAS-hHIPK1 caused less severe malformations (Fig 4A, S1 Table).…”

“…We have previously showed that using a different UAS-dhipk insertion strain (UAS-Hipk 3M ) that has higher expression levels than the attP40 strain used in this work promotes cell proliferation in the wing imaginal disc [28][29][30]. Therefore, we tested the proliferative potential of each of the UAS-hHIPKs by measuring the size of the dpp>GFP expression domain after transgene expression, since increased proliferation would lead to more GFP-expressing cells.…”