Kaavya Krishna Kumar

All Publications

• Stepwise activation of a metabotropic glutamate receptor. Nature Krishna Kumar, K., Wang, H., Habrian, C., Latorraca, N. R., Xu, J., O'Brien, E. S., Zhang, C., Montabana, E., Koehl, A., Marqusee, S., Isacoff, E. Y., Kobilka, B. K. 2024

  Abstract

  Metabotropic glutamate receptors belong to a family of G protein-coupled receptors that are obligate dimers and possess a large extracellular ligand-binding domain that is linked via a cysteine-rich domain to their 7-transmembrane domain1. Upon activation, these receptors undergo a large conformational change to transmit the ligand binding signal from the extracellular ligand-binding domain to the G protein-coupling 7-transmembrane domain2. In this manuscript, we propose a model for a sequential, multistep activation mechanism of metabotropic glutamate receptor subtype 5. We present a series of structures in lipid nanodiscs, from inactive to fully active, including agonist-bound intermediate states. Further, using bulk and single-molecule fluorescence imaging, we reveal distinct receptor conformations upon allosteric modulator and G protein binding.

  View details for DOI 10.1038/s41586-024-07327-x

  View details for PubMedID 38632403

  View details for PubMedCentralID 6709600

• Structural basis for activation of CB1 by an endocannabinoid analog. Nature communications Krishna Kumar, K., Robertson, M. J., Thadhani, E., Wang, H., Suomivuori, C. M., Powers, A. S., Ji, L., Nikas, S. P., Dror, R. O., Inoue, A., Makriyannis, A., Skiniotis, G., Kobilka, B. 2023; 14 (1): 2672

  Abstract

  Endocannabinoids (eCBs) are endogenous ligands of the cannabinoid receptor 1 (CB1), a G protein-coupled receptor that regulates a number of therapeutically relevant physiological responses. Hence, understanding the structural and functional consequences of eCB-CB1 interactions has important implications for designing effective drugs targeting this receptor. To characterize the molecular details of eCB interaction with CB1, we utilized AMG315, an analog of the eCB anandamide to determine the structure of the AMG315-bound CB1 signaling complex. Compared to previous structures, the ligand binding pocket shows some differences. Using docking, molecular dynamics simulations, and signaling assays we investigated the functional consequences of ligand interactions with the "toggle switch" residues F2003.36 and W3566.48. Further, we show that ligand-TM2 interactions drive changes to residues on the intracellular side of TM2 and are a determinant of efficacy in activating G protein. These intracellular TM2 rearrangements are unique to CB1 and are exploited by a CB1-specific allosteric modulator.

  View details for DOI 10.1038/s41467-023-37864-4

  View details for PubMedID 37160876

  View details for PubMedCentralID PMC10169858

• The ubiquitination status of the glucagon receptor determines signal bias. The Journal of biological chemistry Kaur, S., Sokrat, B., Capozzi, M. E., El, K., Bai, Y., Jazic, A., Han, B., Krishna Kumar, K., D'Alessio, D. A., Campbell, J. E., Bouvier, M., Shenoy, S. K. 2023; 299 (5): 104690

  Abstract

  The pancreatic hormone glucagon activates the glucagon receptor (GCGR), a class B seven-transmembrane G protein-coupled receptor that couples to the stimulatory heterotrimeric G protein and provokes PKA-dependent signaling cascades vital to hepatic glucose metabolism and islet insulin secretion. Glucagon-stimulation also initiates recruitment of the endocytic adaptors, βarrestin1 and βarrestin2, which regulate desensitization and internalization of the GCGR. Unlike many other G protein-coupled receptors, the GCGR expressed at the plasma membrane is constitutively ubiquitinated and upon agonist-activation, internalized GCGRs are deubiquitinated at early endosomes and recycled via Rab4-containing vesicles. Herein we report a novel link between the ubiquitination status and signal transduction mechanism of the GCGR. In the deubiquitinated state, coupling of the GCGR to Gs is diminished, while binding to βarrestin is enhanced with signaling biased to a βarrestin1-dependent p38 mitogen activated protein kinase (MAPK) pathway. This ubiquitin-dependent signaling bias arises through the modification of lysine333 (K333) on the cytoplasmic face of transmembrane helix V. Compared with the GCGR-WT, the mutant GCGR-K333R has impaired ubiquitination, diminished G protein coupling, and PKA signaling but unimpaired potentiation of glucose-stimulated-insulin secretion in response to agonist-stimulation, which involves p38 MAPK signaling. Both WT and GCGR-K333R promote the formation of glucagon-induced βarrestin1-dependent p38 signaling scaffold that requires canonical upstream MAPK-Kinase3, but is independent of Gs, Gi, and βarrestin2. Thus, ubiquitination/deubiquitination at K333 in the GCGR defines the activation of distinct transducers with the potential to influence various facets of glucagon signaling in health and disease.

  View details for DOI 10.1016/j.jbc.2023.104690

  View details for PubMedID 37037304

• Negative allosteric modulation of the glucagon receptor by RAMP2. Cell Krishna Kumar, K., O'Brien, E. S., Habrian, C. H., Latorraca, N. R., Wang, H., Tuneew, I., Montabana, E., Marqusee, S., Hilger, D., Isacoff, E. Y., Mathiesen, J. M., Kobilka, B. K. 2023; 186 (7): 1465-1477.e18

  Abstract

  Receptor activity-modifying proteins (RAMPs) modulate the activity of many Family B GPCRs. We show that RAMP2 directly interacts with the glucagon receptor (GCGR), a Family B GPCR responsible for blood sugar homeostasis, and broadly inhibits receptor-induced downstream signaling. HDX-MS experiments demonstrate that RAMP2 enhances local flexibility in select locations in and near the receptor extracellular domain (ECD) and in the 6th transmembrane helix, whereas smFRET experiments show that this ECD disorder results in the inhibition of active and intermediate states of the intracellular surface. We determined the cryo-EM structure of the GCGR-Gs complex at 2.9 Å resolution in the presence of RAMP2. RAMP2 apparently does not interact with GCGR in an ordered manner; however, the receptor ECD is indeed largely disordered along with rearrangements of several intracellular hallmarks of activation. Our studies suggest that RAMP2 acts as a negative allosteric modulator of GCGR by enhancing conformational sampling of the ECD.

  View details for DOI 10.1016/j.cell.2023.02.028

  View details for PubMedID 37001505

• Negative allosteric modulation of the glucagon receptor by RAMP2 O'Brien, E. S., Kumar, K., Habrian, C., Latorraca, N. R., Wang, H., Tuneew, I., Montabana, E., Marqusee, S., Hilger, D., Isacoff, E. Y., Mathiesen, J. M., Kobilka, B. K. CELL PRESS. 2023: 161A

  View details for Web of Science ID 000989629700786

• Negative allosteric modulation of the glucagon receptor by RAMP2. Biophysical journal O'Brien, E. S., Krishna Kumar, K., Habrian, C., Latorraca, N. R., Wang, H., Tuneew, I., Montabana, E., Marqusee, S., Hilger, D., Isacoff, E. Y., Mathiesen, J. M., Kobilka, B. K. 2023; 122 (3S1): 161a

  View details for DOI 10.1016/j.bpj.2022.11.1023

  View details for PubMedID 36782752

• Conformational transitions of a neurotensin receptor1-Gi1complex. Nature Kato, H. E., Zhang, Y., Hu, H., Suomivuori, C., Kadji, F. M., Aoki, J., Krishna Kumar, K., Fonseca, R., Hilger, D., Huang, W., Latorraca, N. R., Inoue, A., Dror, R. O., Kobilka, B. K., Skiniotis, G. 2019

  Abstract

  Neurotensin receptor1 (NTSR1) is a G-protein-coupled receptor (GPCR) that engages multiple subtypes of G protein, and is involved in the regulation of blood pressure, body temperature, weight and the response to pain. Here we present structures of human NTSR1 in complex with the agonist JMV449 and the heterotrimeric Gi1 protein, at a resolution of 3A. We identify two conformations: a canonical-state complex that is similar to recently reported GPCR-Gi/o complexes (in which the nucleotide-binding pocket adopts moreflexible conformations that may facilitate nucleotide exchange), and a non-canonical state in which the G protein is rotated by about 45degrees relative to the receptor and exhibits a more rigid nucleotide-binding pocket. In the non-canonical state, NTSR1 exhibits features of both active and inactive conformations, which suggests that the structure may represent an intermediate form along the activation pathway of G proteins. This structural information, complemented by molecular dynamics simulations and functional studies, provides insights into the complex process of G-protein activation.

  View details for DOI 10.1038/s41586-019-1337-6

  View details for PubMedID 31243364

• Selective modulation of the cannabinoid type 1 (CB1) receptor as an emerging platform for the treatment of neuropathic pain. MedChemComm Banister, S. D., Krishna Kumar, K., Kumar, V., Kobilka, B. K., Malhotra, S. V. 2019; 10 (5): 647-659

  Abstract

  Neuropathic pain is caused by a lesion or dysfunction in the nervous system, and it may arise from illness, be drug-induced or caused by toxin exposure. Since the discovery of two G-protein-coupled cannabinoid receptors (CB1 and CB2) nearly three decades ago, there has been a rapid expansion in our understanding of cannabinoid pharmacology. This is currently one of the most active fields of neuropharmacology, and interest has emerged in developing cannabinoids and other small molecule modulators of CB1 and CB2 as therapeutics for neuropathic pain. This short review article provides an overview of the chemotypes currently under investigation for the development of novel neuropathic pain treatments targeting CB1 receptors.

  View details for DOI 10.1039/c8md00595h

  View details for PubMedID 31191856

  View details for PubMedCentralID PMC6533890

• Selective modulation of the cannabinoid type 1 (CB1) receptor as an emerging platform for the treatment of neuropathic pain MEDCHEMCOMM Banister, S. D., Kumar, K., Kumar, V., Kobilka, B. K., Malhotra, S. V. 2019; 10 (5): 647–59

  View details for DOI 10.1039/c8md00595h

  View details for Web of Science ID 000468790800002

• Structure of a Signaling Cannabinoid Receptor 1-G Protein Complex CELL Kumar, K., Shalev-Benami, M., Robertson, M. J., Hu, H., Banister, S. D., Hollingsworth, S. A., Latorraca, N. R., Kato, H. E., Hilger, D., Maeda, S., Weis, W. I., Farrens, D. L., Dror, R. O., Malhotra, S. V., Kobilka, B. K., Skiniotis, G. 2019; 176 (3): 448-+

  View details for DOI 10.1016/j.cell.2018.11.040

  View details for Web of Science ID 000456526100007

• Structure of a Signaling Cannabinoid Receptor 1-G Protein Complex. Cell Krishna Kumar, K., Shalev-Benami, M., Robertson, M. J., Hu, H., Banister, S. D., Hollingsworth, S. A., Latorraca, N. R., Kato, H. E., Hilger, D., Maeda, S., Weis, W. I., Farrens, D. L., Dror, R. O., Malhotra, S. V., Kobilka, B. K., Skiniotis, G. 2018

  Abstract

  Cannabis elicits its mood-enhancing and analgesic effects through the cannabinoid receptor 1 (CB1), aG protein-coupled receptor (GPCR) that signals primarily through the adenylyl cyclase-inhibiting heterotrimeric G protein Gi. Activation of CB1-Gi signaling pathways holds potential for treating a number of neurological disorders and is thus crucial to understand the mechanism of Gi activation by CB1. Here, we present the structure of the CB1-Gi signaling complex bound to the highly potent agonist MDMB-Fubinaca (FUB), a recently emerged illicit synthetic cannabinoid infused in street drugs that have been associated with numerous overdoses and fatalities. The structure illustrates how FUB stabilizes the receptor in an active state to facilitate nucleotide exchange in Gi. The results compose the structural framework to explain CB1 activation by different classes of ligands and provide insights into the G protein coupling and selectivity mechanisms adopted by the receptor.

  View details for PubMedID 30639101