DNAJC3 deficiency induces β-cell mitochondrial apoptosis and causes syndromic young-onset diabetes

Abstract

Objective: DNAJC3, also known as P58IPK, is an Hsp40 family member that interacts with and inhibits PKR-like ER-localized eIF2α kinase (PERK). Dnajc3 deficiency in mice causes pancreatic β-cell loss and diabetes. Loss-of-function mutations in DNAJC3 cause early-onset diabetes and multisystemic neurodegeneration. The aim of our study was to investigate the genetic cause of early-onset syndromic diabetes in two unrelated patients, and elucidate the mechanisms of β-cell failure in this syndrome. Methods: Whole exome sequencing was performed and identified variants were confirmed by Sanger sequencing. DNAJC3 was silenced by RNA interference in INS-1E cells, primary rat β-cells, human islets, and induced pluripotent stem cell-derived β-cells. β-cell function and apoptosis were assessed, and potential mediators of apoptosis examined. Results: The two patients presented with juvenile-onset diabetes, short stature, hypothyroidism, neurodegeneration, facial dysmorphism, hypoacusis, microcephaly and skeletal bone deformities. They were heterozygous compound and homozygous for novel loss-of-function mutations in DNAJC3. DNAJC3 silencing did not impair insulin content or secretion. Instead, the knockdown induced rat and human β-cell apoptosis and further sensitized cells to endoplasmic reticulum stress, triggering mitochondrial apoptosis via the pro-apoptototic Bcl-2 proteins BIM and PUMA. Conclusions: This report confirms previously described features and expands the clinical spectrum of syndromic DNAJC3 diabetes, one of the five monogenic forms of diabetes pertaining to the PERK pathway of the endoplasmic reticulum stress response. DNAJC3 deficiency may lead to β-cell loss through BIM- and PUMA-dependent activation of the mitochondrial pathway of apoptosis.

Intracellular Lipid Accumulation and Mitochondrial Dysfunction Accompanies Endoplasmic Reticulum Stress Caused by Loss of the Co-chaperone DNAJC3

“…Although DNAJC3 has been widely acknowledged in the attenuation of proteins involved in the initial ER response (Schorr et al, 2015), changes in ER morphology or increased ER calcium leakage were not described previously in the context of the underlying pathophysiology (Synofzik et al, 2014). However, an increased sensitivity against additional ER stress burden was identified in DNAJC3-silenced rat and human β cells (Lytrivi et al, 2021). In accordance with these previous observations, our findings suggest only a minor UPR-activation mirrored by the altered abundance of ER-stress-related proteins (Figure 3).…”

“…GGA1, ADP-ribosylation factor-binding protein GGA1; SMARCB1, SWI/SNF-related matrix-associated actin-dependent regulator of chromatin subfamily B member 1; SDHB, succinate dehydrogenase; SOAT1, Sterol O-acyltransferase 1; CHMP6, charged multivesicular body protein 6; ACADSB, short/branched chain specific acyl-CoA dehydrogenase; ETHE1, persulfide dioxygenase ETHE1; SERPINE2, Glia-derived nexin; PLPP1, phospholipid phosphatase 1; PLIN2, perilipin-2; PTRH2, peptidyl-tRNA hydrolase 2; AARS, alanine-tRNA ligase, cytoplasmic; ALAD, delta-aminolevulinic acid dehydratase; SYNPO2, synaptopodin-2; OCIAD2, OCIA domain-containing protein 2; SF3B4, splicing factor 3B subunit 4; HTATSF1, HIV tat-specific factor 1; APOOL, MICOS complex subunit MIC27; ADD3, gamma-adducin; DNAJC3, DnaJ homolog subfamily C member 3. the secretory machinery, DNAJC3 mutant fibroblasts exhibit ER dysfunction (Synofzik et al, 2014). An increased sensitivity against additional ER stress burden was identified in DNAJC3silenced rat and human β cells (Lytrivi et al, 2021). Notably, several publications demonstrated that cellular cholesterol accumulation leads to UPR activation (Feng et al, 2003;Cunha et al, 2008;Fu et al, 2011).…”

“…Studies of primary patient-derived fibroblasts revealed loss of the DNAJC3 protein and a structurally normal ER, and upon ER stress induction, only minor changes were observed in protein secretion and Ca 2+ leakage (Synofzik et al, 2014). Studies on DNAJC3-silenced rat and human β cells did not affect insulin content and secretion but sensitized cells to ER stress, triggering mitochondrial apoptosis (Lytrivi et al, 2021). To further unravel this pathophysiological route here, we focused on elucidating the pathomechanism of DNAJC3-related pathology by performing proteomics in patient-derived primary fibroblasts, a suitable model to study the etiology of rare neurological diseases (Hentschel et al, 2021), and further investigation of the suggested cellular phenotype.…”

“…The p.His238Asn mutation caused minor decrease in DNAJC3 expression, in contrast to the apparent absence seen in the other reported cases. Moreover, two DNAJC3 patients presenting with juvenile-onset diabetes, short stature, hypothyroidism, neurodegeneration, facial dysmorphism, hypoacusis, microcephaly, and skeletal bone deformities were described (Lytrivi et al, 2021). Symptoms resulting from mutations in DNAJC3 are partially overlapping with phenotypes caused by mutations in DNAJB2 and SIL1, but with the addition of diabetes (Bublitz et al, 2017).…”

GWAS Hits for Bilateral Convergent Strabismus with Exophthalmos in Holstein Cattle Using Imputed Sequence Level Genotypes

“…This gene has been mainly implicated in the development of diabetes [ 37 , 38 ], but also neurodegeneration [ 37 ]. The pathomechanism of diabetes caused by DNAJC3 mutations further involves mitochondrial degeneration [ 39 ]. Thus, it could be also speculated that this gene might be functionally linked to the development of BCSE in cattle.…”