Biology subjects

Allam, R.

Publications and source records attributed to Allam, R..

3 recordsLinked to original sources

bioRxiv2024

Ribonuclease Inhibitor and Angiogenin collaboratively regulate cell-type-specific global translation

Translation of mRNAs is a fundamental process that occurs in all cell-types of multicellular organisms. Conventionally, it has been considered a default step in gene expression, lacking specific regulation. However, recent studies have documented that certain mRNAs exhibit cell-type-specific translation1-3. Despite this, it remains unclear whether global translation is controlled in a cell-type-specific manner. Here we report that a ribosome-associated protein ribonuclease inhibitor-1 (RNH1) and its binding partner Angiogenin (ANG) collaboratively regulates cell-type-specific global translation. By employing human cell-lines and mouse models, we found that deletion of RNH1 decreases global translation selectively in hematopoietic origin cells but not in the non-hematopoietic origin cells. RNH1 mediated such cell-type-specific translation is mechanistically linked to ANG. We found that ANG, which is known to regulate ribosomal biogenesis4, is predominantly expressed in non-hematopoietic origin cells and absent in hematopoietic origin cells. ANG safeguards the non-hematopoietic origin cells from RNH1-knockout-mediated translation defects by upregulating ribosomal biogenesis. Further, we discovered that RNH1 controls the translation of ribosomal protein (RP) transcripts and influences mRNA circularization. Collectively, this study unravels the existence of cell-type-specific global translation regulators and highlights the complex translation regulation in vertebrates.

biochemistry↗

bioRxiv2022

Heightened NLRP3 inflammasome activation is associated with aging and CMML diseases severity

Aging causes chronic low-grade inflammation known as inflamm-aging. It is a risk factor for chronic myelomonocytic leukemia (CMML), a hematological malignancy that is most prevalent in older people. Recent studies suggest a critical role for the NLRP3 inflammasome in inflamm-aging. However, the mechanisms involved in NLRP3 activation in aging and its involvement in CMML progression are not fully understood. Here, we report that aging increases interleukin-1{beta} production upon NLRP3 activation in human CD14+ monocytes. Interestingly, we found that Toll-like receptor (TLR) 1/2 agonist Pam3Cysk4 directly activates NLRP3 inflammasome without the requirement of second activation signal in monocytes from older but not from younger healthy donors. Further, we observed a dichotomous response to NLRP3 inflammasome activation in monocytes from CMML patients. Intriguingly, CMML patients with heightened NLRP3 activation showed increased treatment dependency and disease severity. Collectively, our results suggest that aging causes increased sensitivity to NLRP3 inflammasome activation at cellular level, which may explain increased inflammation and immune dysregulation in older individuals. Furthermore, NLRP3 inflammasome activation was dysregulated in CMML and positively correlated with disease severity.

immunology↗

bioRxiv2021

LRR protein RNH1 inhibits inflammasome activation through proteasome-mediated degradation of Caspase-1 and is associated with adverse clinical outcomes in COVID-19 patients.

Inflammasomes are cytosolic innate immune sensors of pathogen infection and cellular damage that induce caspase-1 mediated inflammation upon activation. Although inflammation is protective, uncontrolled excessive inflammation can cause inflammatory diseases and can be detrimental, such as in COVID-19. However, the underlying mechanisms that control inflammasome activation are incompletely understood. Here we report that the leucine rich repeat (LRR) protein Ribonuclease inhibitor (RNH1), which shares homology with LRRs of NLRP proteins, attenuates inflammasome activation. Deletion of RNH1 in macrophages increases IL-1{beta} production and caspase-1 activation for inflammasome stimuli. Mechanistically, RNH1 decreases pro-IL-1{beta} expression and induces proteasome-mediated caspase-1 degradation. Corroborating this, mouse models of monosodium urate (MSU)-induced peritonitis and LPS-induced endotoxemia, which are dependent on caspase-1, respectively show increased neutrophil infiltration and lethality in Rnh1-/- mice compared to WT mice. Furthermore, RNH1 protein levels are negatively correlated with inflammation and disease severity in hospitalized COVID-19 patients. We propose that RNH1 is a new inflammasome regulator with relevance to COVID-19 severity.

immunology↗