Sse1, Hsp110 chaperone of yeast, controls the cellular fate during endoplasmic reticulum stress.

Sse1 is a cytosolic Hsp110 molecular chaperone of yeast, Saccharomyces cerevisiae. Its multifaceted roles in cellular protein homeostasis as a nucleotide exchange factor (NEF), as a protein-disaggregase and as a chaperone linked to protein synthesis (CLIPS) are well documented. In the current study, we show that SSE1 genetically interacts with IRE1 and HAC1, the endoplasmic reticulum-unfolded protein response (ER-UPR) sensors implicating its role in ER protein homeostasis. Interestingly, the absence of this chaperone imparts unusual resistance to tunicamycin-induced ER stress which depends on the intact Ire1-Hac1 mediated ER-UPR signaling. Furthermore, cells lacking SSE1 show inefficient ER-stress-responsive reorganization of translating ribosomes from polysomes to monosomes that drive uninterrupted protein translation during tunicamycin stress. In consequence, the sse1Δ strain shows prominently faster reversal from ER-UPR activated state indicating quicker restoration of homeostasis, in comparison to the wild-type (WT) cells. Importantly, Sse1 plays a critical role in controlling the ER-stress-mediated cell division arrest, which is escaped in sse1Δ strain during chronic tunicamycin stress. Accordingly, sse1Δ strain shows significantly higher cell viability in comparison to WT yeast imparting the stark fitness following short-term as well as long-term tunicamycin stress. These data, all together, suggest that cytosolic chaperone Sse1 is an important modulator of ER stress response in yeast and it controls stress-induced cell division arrest and cell death during overwhelming ER stress induced by tunicamycin.

Spectrum of Primary Immunodeficiency Disorders in Hospitalized Children: Multicentric Data From Kolkata.

OBJECTIVE: To evaluate the incidence and types of primary immunodeficiency diseases (PIDs) in hospitalized children with infection. METHODS: This prospective study was conducted in five tertiary-care facilities in Kolkata over two consecutive years between November 1, 2018 and October 31, 2020. We included all children aged upto 12years who were hospitalized and screened them for PID. Children were screened for suspected IPD using Jeffrey Modell Foundation (JMF) Criteria; any child who satisfied at least 2 out of 10 warning signs was further evaluated for PIDs. RESULTS: Out of 33,204 hospital admissions, 50 children satisfied JMF criteria. Out of 50 children screened during the study period, 27 were finally diagnosed with an underlying PID, with a prevalence of 1 in 1000 hospitalized children. Majority (37.03%) of them had antibody deficiency followed by phagocytic defect (33.3%). Chronic granulomatous disease was the commonest PID followed by common variable immunodeficiency. Around 62.97% children presented with respiratory infections and overall Acinetobacter baumannii was the commonest isolated organism. CONCLUSION: Our study presents the first cohort of PID from eastern India. A methodical step-wise clinical and diagnostic approach can facilitate early diagnosis and timely therapeutic interventions.