Biology subjects

Ramamurthy, B.

Publications and source records attributed to Ramamurthy, B..

4 recordsLinked to original sources

bioRxiv2025

The C. elegans WASH complex supports epithelial polarity by promoting endosomal sorting of Cadherin

Epithelial polarity requires polarized distribution of the apical adhesion complex that connects cells through the Cadherin transmembrane protein. Cadherin is intimately linked to the actin cytoskeleton through alpha catenin, which directly binds F-actin to set up the apical actin belt. Branched actin is formed when the Arp2/3 complex is activated by Nucleation Promoting Factors. C. elegans has three Nucleation Promoting Factors, WASP, WAVE and WASH. Our studies showed that WAVE-dependent branched actin promotes apical transport of Cadherin, including apically-directed transport of RAB-11-enriched endosomes. However, the contribution of other Nucleation Promoting Factors to Cadherin polarity has not been examined. The C. elegans WASH complex is not well described. Here we characterize components of the WASH complex, and confirm that CO5G5.2, despite being highly divergent, is the functional FAM21 component in C. elegans. We show that the WASH complex is enriched at early and recycling endosomes in the adult intestine, where it supports retrograde Cadherin transport. Our findings demonstrate that individual branched actin regulators promote specific transport steps, and identify WASH function at RME-1/EHD-enriched endosomes as an important contributor to Cadherin polarity and cargo sorting in a mature epithelium. Significance Statement*C. elegans has three known NPF (nucleation promoting factor) complexes to activate Arp2/3: WAVE, WASP and WASH. However, the role of C. elegans WASH complex in intracellular transport was unreported, and the essential component, FAM21, was not identified. *We show that C. elegans C05G5.2 is a likely FAM21 ortholog, since it functions in collaboration with other WASH components in retrograde transport. Loss of WASH components reduced epithelial polarity, while the cargo Cadherin was mis-sorted from early endosomes. *WASH branched actin polarizes epithelia using a functional FAM21 ortholog to promote sorting of retrograde cargo, including Cadherin.

cell biology↗

bioRxiv2024

Extracellular adenosine deamination primes tip organizer development in Dictyostelium

Ammonia is a morphogen in Dictyostelium and is known to arise from the catabolism of proteins and RNA. However, we show that extracellular adenosine deamination catalyzed by adenosine deaminase related growth factor (ADGF), is a major source of ammonia, and demonstrate a direct role of ammonia in tip organizer development. The tip formed during early development in Dictyostelium functions analogously to the embryonic organizer of higher vertebrates. Dictyostelium cell lines carrying mutations in the gene adgf fail to establish an organizer, and this could be reversed by exposing the mutants to volatile ammonia. Interestingly, Klebsiella pneumoniae physically separated from the Dictyostelium adgf mutants in a partitioned dish, also rescues the mound arrest phenotype suggesting a cross-kingdom interaction that drives development. Both the substrate, adenosine and the product, ammonia regulate adgf expression, and ADGF acts downstream of the histidine kinase DhkD in regulating tip formation. Thus, the consecutive transformation of extracellular cAMP to adenosine, and adenosine to ammonia are integral steps during Dictyostelium development. Remarkably, in higher vertebrates, adgf expression is elevated during gastrulation and thus adenosine deamination may be a conserved process driving organizer development in different organisms.

developmental biology↗

bioRxiv2022

Persistence of parental age effect on somatic mutation rates across generations in Arabidopsis.

In the model plant Arabidopsis thaliana, parental age is known to affect somatic mutation rates in their immediate progeny and here we show that this age dependent effect persists across successive generations. Using a set of detector lines carrying the mutated uidA gene, we examined if a particular parental age maintained across five consecutive generations affected the rates of base substitution (BSR), intrachromosomal recombination (ICR), frameshift mutation (FS), and transposition. The frequency of functional GUS reversions were assessed in seedlings as a function of identical/different parental ages across generations. In the context of a fixed parental age, BCR/ICR rates were unaffected in the first three generations, then dropped significantly in the 4th and increased in most instances in the 5th generation. On the other hand, with advancing parental ages, BSR/ICR rates remained high in the first two/three generations, with a striking resemblance in the pattern of mutation rates. We adopted a novel approach of identifying and tagging flowers pollinated on a particular day, thereby avoiding biases due to potential emasculation induced stress responses. Our results suggest a time component in counting the number of generations a plant has passed through self-fertilization at a particular age in determining the somatic mutation rates.

developmental biology↗

bioRxiv2021

LY-CoV1404 potently neutralizes SARS-CoV-2 variants

SARS-CoV-2 neutralizing monoclonal antibodies (mAbs) can reduce the risk of hospitalization when administered early during COVID-19 disease. However, the emergence of variants of concern has negatively impacted the therapeutic use of some authorized mAbs. Using a high throughput B-cell screening pipeline, we isolated a highly potent SARS-CoV-2 spike glycoprotein receptor binding domain (RBD)-specific antibody called LY-CoV1404 (also known as bebtelovimab). LY-CoV1404 potently neutralizes authentic SARS-CoV-2 virus, including the prototype, B.1.1.7, B.1.351 and B.1.617.2). In pseudovirus neutralization studies, LY-CoV1404 retains potent neutralizing activity against numerous variants including B.1.1.7, B.1.351, B.1.617.2, B.1.427/B.1.429, P.1, B.1.526, B.1.1.529, and the BA.2 subvariant and retains binding to spike proteins with a variety of underlying RBD mutations including K417N, L452R, E484K, and N501Y. Structural analysis reveals that the contact residues of the LY-CoV1404 epitope are highly conserved with the exception of N439 and N501. Notably, the binding and neutralizing activity of LY-CoV1404 is unaffected by the most common mutations at these positions (N439K and N501Y). The breadth of reactivity to amino acid substitutions present among current VOC together with broad and potent neutralizing activity and the relatively conserved epitope suggest that LY-CoV1404 has the potential to be an effective therapeutic agent to treat all known variants causing COVID-19. In BriefLY-CoV1404 is a potent SARS-CoV-2-binding antibody that neutralizes all known variants of concern and whose epitope is rarely mutated. HighlightsO_LILY-CoV1404 potently neutralizes SARS-CoV-2 authentic virus and known variants of concern including the B.1.1.529 (Omicron), the BA.2 Omicron subvariant, and B.1.617.2 (Delta) variants C_LIO_LINo loss of potency against currently circulating variants C_LIO_LIBinding epitope on RBD of SARS-CoV-2 is rarely mutated in GISAID database C_LIO_LIBreadth of neutralizing activity and potency supports clinical development C_LI

immunology↗