DYRK1A regulates Hap1–Dcaf7/WDR68 binding with implication for delayed growth in Down syndrome

Abstract

Huntingtin-associated protein 1 (Hap1) is known to be critical for postnatal hypothalamic function and growth. Hap1 forms stigmoid bodies (SBs), unique neuronal cytoplasmic inclusions of unknown function that are enriched in hypothalamic neurons. Here we developed a simple strategy to isolate the SB-enriched fraction from mouse brain. By analyzing Hap1 immunoprecipitants from this fraction, we identified a Hap1-interacting SB component, DDB1 and CUL4 associated factor 7 (Dcaf7)/WD40 repeat 68 (WDR68), whose protein level and nuclear translocation are regulated by Hap1. Moreover, we found that Hap1 bound Dcaf7 competitively in cytoplasm with dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A), a protein implicated in Down syndrome (DS). Depleting Hap1 promoted the DYRK1A-Dcaf7 interaction and increased the DYRK1A protein level. Transgenic DS mice overexpressing DYRK1A showed reduced Hap1-Dcaf7 association in the hypothalamus. Furthermore, the overexpression of DYRK1A in the hypothalamus led to delayed growth in postnatal mice, suggesting that DYRK1A regulates the Hap1-Dcaf7 interaction and postnatal growth and that targeting Hap1 or Dcaf7 could ameliorate growth retardation in DS.H untingtin-associated protein 1 (Hap1) is a cytoplasmic protein highly expressed in neurons of the CNS (1, 2). Hap1 was initially recognized for its binding to polyglutamine-expanded huntingtin (Htt), the protein responsible for Huntington's disease (3). Because Hap1 is expressed at various levels in different types of neurons (1,(4)(5)(6)(7)(8), it is likely involved in cell type-specific functions of the brain. For example, Hap1 is abundantly expressed in the hypothalamus, and its expression in the hypothalamus influences the central control of feeding (9); as a direct result, mice lacking Hap1 are malnourished and die in the early postnatal period (5, 10, 11). The function of Hap1 is also age dependent and appears to be important for postnatal neurogenesis in the paraventricular nuclei, the lateral hypothalamus (5, 11), and the dentate gyrus of the hippocampus (7).The specific function of Hap1 in the hypothalamus may be associated with unique cytoplasmic structures called "stigmoid bodies" (SBs), which are formed by Hap1 in the hypothalamus (12, 13) and appear to be non-membrane-bound, ovoid to circular in shape, and 0.5-3 μm in diameter (14,15). Widely regarded as a determinant marker for SBs, Hap1 is capable of sequestering several important disease-related proteins into SB-like inclusions in cell cultures, including Abelson helper integration site 1 (Ahi1), androgen receptor, TBP, and ataxin-3 (6, 16-18). However, in vivo evidence for such sequestration exists only for Ahi1, which is responsible for specific forms of Joubert syndrome. Other proteins, such as SorLA/LR11, sortilin, 5-HT 7 receptor, and 14-3-3, are also reported to be associated with . Although SBs are abundant in the hypothalamus, their functions remain elusive, despite speculation that they might be involved in sex-steroid maturation (15). We bel...

Synergistic Toxicity of Polyglutamine-Expanded TATA-Binding Protein in Glia and Neuronal Cells: Therapeutic Implications for Spinocerebellar Ataxia 17

“…Data are represented as mean Ϯ SEM. ***p Ͻ 0.001. known to produce multiple proinflammatory molecules (Sofroniew, 2015). Given all the evidence, our present study establishes inflammatory activation in the astrocytes as a major contributor to the pathogenesis of SCA17.…”

“…Among these diseases, SCA17 is caused by Ͼ42 CAG repeats in the TATA box-binding protein (TBP) gene (Koide et al, 1999;Nakamura et al, 2001), which encodes a general transcription factor that plays critical roles in transcriptional initiation (Nikolov and Burley, 1994). SCA17 patients show late-onset symptoms that include ataxia, dystonia, parkinsonism, and psychiatric abnormalities, accompanied by progressive neurodegeneration in the cerebellum (Koide et al, 1999;Nakamura et al, 2001;Rolfs et al, 2003;Bauer et al, 2004;Bruni et al, 2004;Toyoshima et al, 2004). Although the exact pathological mechanisms of SCA17 remain elusive, emerging evidence indicates that transcriptional dysregulation caused by mutant TBP represents a major form of toxicity .…”

“…Nonetheless, in recent years, research has revealed that glia, the most abundant cells in the CNS and which provide support and protection for neurons, are also actively involved in the pathogenesis of polyQ diseases. For example, in Huntington's disease, the expression of mutant huntingtin (htt) in glial cells can lead to the development of Huntington's disease phenotypes in mice (Shin et al, 2005;Bradford et al, 2009;Tong et al, 2014;B. Huang et al, 2015;Oliveira et al, 2016).…”

The adaptor proteins HAP1a and GRIP1 collaborate to activate the kinesin-1 isoform KIF5C

“…2A for singly transfected cells). Puncta are likely related to an endogenous non-membranebound organelle formed by HAP1; within the hypothalamus, HAP1 is highly expressed (Chan et al, 2002;Li et al, 2003;Sheng et al, 2006) and associated with non-membrane-bound cytoplasmic bodies (Li et al, 1998;Shinoda et al, 1992Shinoda et al, , 1993Xiang et al, 2017) that sequester several key proteins in culture (Prigge and Schmidt, 2007;Rong et al, 2007;Sheng et al, 2008;Takeshita et al, 2011Takeshita et al, , 2006. When co-expressed in the same cells, GRIP1a and HAP1a are recruited to the same intracellular compartment (Fig.…”

MANF regulates hypothalamic control of food intake and body weight

“…Method for immunoprecipitation was described previously 56 , 57 . Briefly, cell or brain lysates were homogenized in NP-40 buffer (50 mM NaCl, 50 mM Tris–HCl pH8.0, 0.1% Triton X-100, 0.5% NP-40), and 300 μg of protein was used for one experiment.…”