Kalichamy, Karunambigai et al. (2021) International Worm Meeting "C. elegans prk mutants exhibit pleiotropic defects."

Kalichamy, Karunambigai, L Hudson, Martin, J Koskinen, Paivi, Tuomaala, Joel

[International Worm Meeting, 2021]

The mammalian PIM family of serine/threonine kinases regulate several cellular functions, such as cell survival and motility. In behavioral studies of C. elegans nematodes, we have observed that the PIM-related kinases (PRKs) are essential for chemotactic movements of the animals in response to olfactory stimuli sensed by AWB and AWCON neurons (Kalichamy et al., 2019). When analyzing prk-deficient mutants, prk-1(pk86) and prk-2(ok3069), we noticed that in addition to olfaction, their brood size and growth were also negatively affected. Therefore, we have now analysed the prk expression patterns and the pleiotrophic effects of the mutations in more detail. Morphological analyses have revealed that prk-1 is required for body length, body bends, male tail development and longevity. While a transcriptional fusion reporter of prk-1 is expressed in head neurons and intestine, prk-2 is found from posterior parts of the intestine in L2 to L4 larvae and strongly expressed in intestine and seam cells in young adults to adults. Further genetic analyses are underway to fully elucidate the functional roles of PRKs.

Kalichamy, Karunambigai et al. (2021) International Worm Meeting "Behavioral studies, responses and chemical synapses on EphR/ephrin deficient mutants"

Hill, Tyler, L Hudson, Martin, McCardel, Kerry, Arnold, Miranda, Kalichamy, Karunambigai

[International Worm Meeting, 2021]

In C. elegans, EphR/ephrin signaling pathways play pivotal roles in multiple biological functions, including epidermal morphogenesis, male tail development, cell migration, cell proliferation, cell morphology, neurite outgrowth and germ line apoptosis. Eph receptor, vab-1(dx31) mutants and ephrin ligands, efn-1(e1) and efn-4(bx80) mutant exhibit strong phenotypes like embryonic lethality, larval lethality, notched head, tail deformities and axon guidance cues. The amphid sensory neurons including the olfactory-sensing AWA and AWC neurons, temperature-sensing AFD neurons and gustatory-sensing ASE neurons, send chemical synapses primarily onto the paired AIY interneurons. The AIYs lie posterior to the pharynx and suppress turns and reversal behavior in wild-type nematodes. Ventral AIY neurite morphology is disrupted in vab-1, efn-1 and efn-4 mutants, whereas dorsal extension is disrupted in efn-4 mutant animals. How these neuronal defects affect sensory-to-interneuron physiology and behavior is not known. Preliminary studies on ASE neuron morphology revealed that vab-1 and efn-1 have only a minor role in ASE development, suggesting that distinct axon guidance programs are used for the ASE sensory neurons versus AIY interneurons. However, we find that food seeking behavior is significantly affected in vab-1 and efn-4 mutants when compared to wild-type. These data suggest that EphR/ephrin control of AIY interneuron morphology is required, in part, for correct sensory circuit function.

Kalichamy, Karunambigai et al. (2011) International Worm Meeting "Role of ER resident proteins Calnexin and Calreticulin in Chemosensory Behavior in C. elegans."

Lee, Sunkyung, Kalichamy, Karunambigai, Ahnn, Joohong

[International Worm Meeting, 2011]

Calnexin and calreticulin, lectin chaperone proteins, are calcium binding proteins in Endoplasmic reticulum(ER). These proteins facilitate the proper folding and quality control of newly synthesized glycoproteins that exit from ER. C. elegans, a free-living soil nematode, can detect a wide variety of volatile attractants using their chemosensory amphid neurons. C. elegans homolog's calnexin and calreticulin are expressed in neurons. In order to study the function of calnexin and calreticulin in chemosensory behaviors, we investigated the behavioral phenotype of calnexin (cnx-1) and calreticulin (crt-1) mutants. Both cnx-1 and crt-1 mutants exhibited normal chemotaxis responding to AWC sensed odorants such as isoamyl alcohol, benzaldehyde and butanone. The cnx-1 mutants failed to adapt to AWC sensed odors whereas crt-1 mutants exhibited hyperadaptation, when compared with wildtype. The expression of str-2::GFP in cnx-1 or crt-1 mutant background showed morphological defects in neurons. We are further investigating how these ER resident proteins modulate to the chemosensory behavior and the underlying mechanism.

Karunambigai Kalichamy et al. (2010) East Asia Worm Meeting "Calnexin and Calreticulin are involved in Chemosensory Behavior in C.elegans"

Joohong Ahnn, Karunambigai Kalichamy, Sunkyung Lee

[East Asia Worm Meeting, 2010]

C. elegans are free-living soil nematodes which are able to detect different volatile odorants using their chemosensory olfactory neurons. The olfactory sensation results in adaptation after prolonged exposure of odorants. Calnexin and calreticulin are calcium binding proteins which facilitate protein folding in the endoplasmic reticulum (ER). C. elegans homologs of both calnexin and calreticulin are expressed in neurons, and play essential roles in development and neurodegenerative. Wildtype animals pre-exposed to an odorant reduce the response to the odorant. Mutants for calnexin, cnx-1, and calreticulin, crt-1, can respond robustly to odorants sensed by the AWC chemosensory neurons. However, the crt-1 mutants exhibited hyperadaptation to AWC sensed odors such as isoamyl alcohol, benzaldehyde and butanone when compared to wild type, while cnx-1 mutants failed to adapt to these odors. These results suggest that CNX-1 and CRT-1 may be involved in adaptation of AWC-mediated chemosensation. We are currently investigating the underlying mechanism responsible for experience-dependent behaviors involving AWC neurons requiring either calnexin or calreticulin.

Dwivedi, Meenakshi et al. (2009) International Worm Meeting "Lifespan extension in calcineurin-defective mutants requires autophagy genes in C. elegans."

Ahnn, Joohong, Kalichamy, Karunambigai, Dwivedi, Meenakshi, Wiacek, Magdalena

[International Worm Meeting, 2009]

Lifespan extension in any organism literally means a delay in the aging process. Many of the pathways found to be involved in lifespan regulation in different organisms are dependent on the autophagy pathway or autophagic genes. In Caenorhabditis elegans, the target of rapamycin (TOR) pathway, which is responsible for sensing nutrients (inhibited by dietary restriction) and the insulin/IGF-1 pathway, which responds to different environmental cues, are well known pathways involved in lifespan extension and are reportedly dependent on the autophagy. In addition, it has recently been reported that lifespan extension in mutants with lowered mitochondrial respiration and cep-1 mutants (orthologue of p53) is also dependent on autophagic genes. The results of a study that we conducted also suggested that calcineurin regulates lifespan through the autophagy genes. Calcineurin (CaN) is a serine/threonine phosphatase, activated by Ca2+/calmodulin (Ca2+/CaM). CaN is known to regulate various cellular responses in different organisms. In this study, we report that calcineurin defective strains exhibit enhanced autophagy as assessed by the increased formation of GFP::LGG-1 associated autophagic structures in the seam cells. In addition to enhanced autophagy in calcineurin loss-of-function/null mutants, extended lifespan was also observed in cnb-1(jh103) calcineurin B null mutant and tax-6(ok2065) loss-of-function mutant of calcineurin A when compared to wild-type and tax-6(jh107) gain-of-function mutants. The RNAi knock-down of two essential autophagy genes, bec-1 and atg-7, suppress both the number of autophagic puncta and the lifespan extension observed in the calcineurin-defective mutants. The suppression of lifespan extension to the levels similar to wild-type animals fed with control vector only was observed in both cnb-1(jh103) and tax-6(ok2065) mutants treated with bec-1 RNAi. Thus, for the first time we suggest that pathway operating for lifespan extension in calcineurin mutants converge at the autophagic pathway. This activated autophagic pathway in calcineurin mutants may be due to the disruption in calcium signaling pathway, which remains to be elucidated.