Orthodenticle and Kruppel homolog 1 regulate Drosophila photoreceptor maturation.

Neurons present a wide variety of morphologies that are associated with their specialized functions. However, to date very few pathways and factors regulating neuronal maturation, including morphogenesis, have been identified. To address this issue we make use here of the genetically amenable developing fly photoreceptor (PR). Whereas this sensory neuron is specified early during retinal development, its maturation spans several days. During this time, this neuron acquires specialized membrane domains while undergoing extensive polarity remodeling. In this study, we identify a pathway in which the conserved homeobox protein Orthodenticle (Otd) acts together with the ecdysone receptor (EcR) to directly repress the expression of the transcription factor (TF) Kruppel homolog 1 (Kr-h1). We demonstrate that this pathway is not required to promote neuronal specification but is crucial to regulate PR maturation. PR maturation includes the remodeling of the cell's epithelial features and associated apical membrane morphogenesis. Furthermore, we show that hormonal control coordinates PR differentiation and morphogenesis with overall development. This study demonstrates that during PR differentiation, transient repression of Kr-h1 represents a key step regulating neuronal maturation. Down-regulation of Kr-h1 expression has been previously associated with instances of neuronal remodeling in the fly brain. We therefore conclude that repression of this transcription factor represents a key step, enabling remodeling and maturation in a wide variety of neurons.

Real-world evidence of the use of the infliximab biosimilar SB2: data from the PERFUSE study.

Objective: PERFUSE is a non-interventional study of 1233 adult patients (rheumatology, n = 496; IBD, n = 737) receiving routine infliximab (IFX) biosimilar SB2 therapy. The aim of this report was to investigate the 12-month persistence, effectiveness and safety outcomes of routine SB2 treatment in patients with chronic inflammatory rheumatic disease. Methods: Patients with a diagnosis of RA, PsA or axial spondyloarthritis (axSpA) were assigned to one of three study cohorts according to whether SB2 treatment initiated after September 2017 had been the first IFX treatment (IFX naïve) or followed transition from reference IFX (IFX ref) or another IFX biosimilar (IFX bs). Outcomes to month 12 (±2) included persistence (primary outcome), SB2 dose, disease status, immunogenicity and safety. Results: At month 12, persistence on SB2 in IFX-naïve, IFX ref and IFX bs cohorts, respectively, [mean percentage (95% CI)] by indication was as follows: 59% (36.1, 76.2), 75% (57.5, 86.1) and 85% (69.6, 93.0) for RA (n = 98); 64% (34.3, 83.3), 87% (65.6, 95.7) and 83% (60.0, 93.1) for PsA (n = 62); and 56% (44.4, 66.5), 80% (70.8, 86.1) and 80% (72.5, 85.6) for axSpA (n = 336). Disease activity was comparable at baseline and month 12 within the IFX ref and bs subgroups of all cohorts by indication. No immunogenicity concerns or new safety signals were detected. Conclusion: SB2 was safe and effective in IFX-naïve patients and in patients transitioned from prior IFX ref or bs. Trial registration: clinicaltrials.gov, NCT03662919.

PERFUSE: a French non-interventional study of patients with inflammatory bowel disease receiving infliximab biosimilar SB2: a 12-month analysis.

Background: FlixabiTM (SB2) is a biosimilar of the reference infliximab (IFX), Remicade®. Published evidence on long-term, real-world use of SB2 in patients either IFX naive or transitioned from prior IFX is scarce. Objectives: We evaluated persistence, effectiveness, and safety of SB2 over 12 months in adults with IBD [Crohn's disease (CD) and ulcerative colitis (UC)], participating in PERFUSE. Design: PERFUSE is a long-term, non-interventional, multicenter study of patients receiving SB2 at specialist sites across France. Methods: SB2 treatment was initiated in September 2017, either as first IFX treatment (IFX naive), after transition from treatment with reference IFX (IFX ref) or another IFX biosimilar (IFX bs), or both IFX ref and IFX bs (IFX multiswitch). Outcomes up to Month 12 (±2) include persistence on SB2 (primary outcome measure), SB2 dose, disease status, immunogenicity, and safety. Results: This final 12-month analysis of patients with IBD includes 569 with CD and 168 with UC. Persistence [95% confidence interval (CI)] at Month 12 was CD: 89% (77.2; 94.9), UC: 78.5% (58.2; 89.8) for IFX naive; CD: 94% (91.0; 96.1), UC: 92.8% (84.8; 96.7) for IFX ref; CD: 91.6% (86.0; 95.0), UC: 94.2% (83.1; 98.1) for IFX bs; and CD 100% (100; 100), UC 100% (100; 100) for IFX multiswitch. In the CD and UC cohorts, disease activity among IFX naive patients declined from baseline to Month 12; with any prior IFX, the proportions of patients in remission at baseline, Month 6, and Month 12 remained unchanged in the UC cohort, and were comparable or higher in the CD cohort. No immunogenicity or safety signals were detected. Conclusions: Patients with IBD can be initiated on SB2 or transitioned from IFX ref and/or IFX bs to SB2, with no loss of disease control or safety concerns, with >75% of naive and >90% of transitioned patients continuing on SB2 treatment at 12 months.

Costal2 functions as a kinesin-like protein in the hedgehog signal transduction pathway.

The Hedgehog (Hh) signaling pathway initiates an evolutionarily conserved developmental program required for the proper patterning of many tissues [1]. Although Costal2 (Cos2) is a requisite component of the Hh pathway, its mechanistic role is not well understood. Because of its primary sequence, Cos2 was initially predicted to function as a kinesin-like protein [2]. However, evidence showing that Cos2 function might require kinesin-like properties has been lacking [2-6]. Thus, the prevailing dogma in the field is that Cos2 functions solely as a scaffolding protein [7, 8]. Here, we show that Cos2 motility is required for its biological function and that this motility may be Hh regulated. We show that Cos2 motility requires an active motor domain, ATP, and microtubules. Additionally, Cos2 recruits and transports other components of the Hh signaling pathway, including the transcription factor Cubitus interruptus (Ci). Drosophila expressing cos2 mutations that encode proteins that lack motility are attenuated in their ability to regulate Ci activity and exhibit phenotypes consistent with attenuated Cos2 function [9]. Combined, these results demonstrate that Cos2 motility plays an important role in its function, regulating the amounts and activity of Ci that ultimately interpret the level of Hh to which cells are exposed.

Control of the dynamics and homeostasis of the Drosophila Hedgehog receptor Patched by two C2-WW-HECT-E3 Ubiquitin ligases.

The conserved Hedgehog (HH) signals control animal development, adult stem cell maintenance and oncogenesis. In Drosophila, the HH co-receptor Patched (PTC) controls both HH gradient formation and signalling. PTC is post-translationally downregulated by HH, which promotes its endocytosis and destabilization, but the mechanisms of PTC trafficking and its importance in the control of PTC remain to be understood. PTC interacts with E3 Ubiquitin (UB)-ligases of the C2-WW-HECT family; two of them-SMURF and NEDD4-are known to regulate its levels. We demonstrate that mutation of the PTC PY motif, which mediates binding of C2-WW-HECT family members, inhibits its internalization but not its autonomous and non-autonomous signalling activities. In addition, we show that the two related UB-C2-WW-HECT ligases NEDD4 and SU(DX) regulate PTC trafficking and finely tune its accumulation through partially redundant but distinct functions. While both NEDD4 and SU(DX) promote PTC endocytosis, only SU(DX) is able to induce its lysosomal targeting and degradation. In conclusion, PTC trafficking and homeostasis are tightly regulated by a family of UB-ligases.

The role of ciliary trafficking in Hedgehog receptor signaling.

Defects in the biogenesis of or transport through primary cilia affect Hedgehog protein signaling, and many Hedgehog pathway components traffic through or accumulate in cilia. The Hedgehog receptor Patched negatively regulates the activity and ciliary accumulation of Smoothened, a seven-transmembrane protein that is essential for transducing the Hedgehog signal. We found that this negative regulation of Smoothened required the ciliary localization of Patched, as specified either by its own cytoplasmic tail or by provision of heterologous ciliary localization signals. Surprisingly, given that Hedgehog binding promotes the exit of Patched from the cilium, we observed that an altered form of Patched that is retained in the cilium nevertheless responded to Hedgehog, resulting in Smoothened activation. Our results indicate that whereas ciliary localization of Patched is essential for suppression of Smoothened activation, the primary event enabling Smoothened activation is binding of Hedgehog to Patched, and Patched ciliary removal is secondary.

The last 59 amino acids of Smoothened cytoplasmic tail directly bind the protein kinase Fused and negatively regulate the Hedgehog pathway.

The Hedgehog (HH) signaling pathway is crucial for the development of many organisms and its inappropriate activation is involved in numerous cancers. HH signal controls the traffic and activity of the seven-pass transmembrane protein Smoothened (SMO), leading to the transcriptional regulation of HH-responsive genes. In Drosophila, the intracellular transduction events following SMO activation depend on cytoplasmic multimeric complexes that include the Fused (FU) protein kinase. Here we show that the regulatory domain of FU physically interacts with the last 52 amino acids of SMO and that the two proteins colocalize in vivo to vesicles. The deletion of this region of SMO leads to a constitutive activation of SMO, promoting the ectopic transcription of HH target genes. This activation is partially dependent of FU activity. Thus, we identify a novel link between SMO and the cytoplasmic complex(es) and reveal a negative role of the SMO C-terminal region that interacts with FU. We propose that FU could act as a switch, activator in presence of HH signal or inhibitor in absence of HH.