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Mondal S, Botterbusch S, Narayan K, Powers I, Zheng J, Baumgart T. Multivalent interactions between molecular components involved in non-clathrin endocytosis drive protein phase separation. Biophys J 2022. [DOI: 10.1016/j.bpj.2021.11.2319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Abstract
Liquid-liquid phase separation has recently emerged as an important fundamental organizational phenomenon in biological settings. Most studies of biological phase separation have focused on droplets that "condense" from solution above a critical concentration, forming so-called "membraneless organelles" suspended in solution. However, membranes are ubiquitous throughout cells, and many biomolecular condensates interact with membrane surfaces. Such membrane-associated phase-separated systems range from clusters of integral or peripheral membrane proteins in the plane of the membrane to free, spherical droplets wetting membrane surfaces to droplets containing small lipid vesicles. In this review, we consider phase-separated liquids that interact with membrane surfaces and we discuss the consequences of those interactions. The physical properties of distinct liquid phases in contact with bilayers can reshape the membrane, and liquid-liquid phase separation can construct membrane-associated protein structures, modulate their function, and organize collections of lipid vesicles dynamically. We summarize the common phenomena that arise in these systems of liquid phases and membranes.
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Mondal S, Narayan KB, Powers I, Botterbusch S, Baumgart T. Endophilin recruitment drives membrane curvature generation through coincidence detection of GPCR loop interactions and negative lipid charge. J Biol Chem 2021; 296:100140. [PMID: 33268381 PMCID: PMC7948419 DOI: 10.1074/jbc.ra120.016118] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2020] [Revised: 11/25/2020] [Accepted: 12/01/2020] [Indexed: 12/23/2022] Open
Abstract
Endophilin plays key roles during endocytosis of cellular receptors, including generating membrane curvature to drive internalization. Electrostatic interactions between endophilin's BIN/Amphiphysin/Rvs domain and anionic membrane lipids have been considered the major driving force in curvature generation. However, the SH3 domain of endophilin also interacts with the proline-rich third intracellular loop (TIL) of various G-protein-coupled receptors (GPCRs), and it is unclear whether this interaction has a direct role in generating membrane curvature during endocytosis. To examine this, we designed model membranes with a membrane density of 1400 receptors per μm2 represented by a covalently conjugated TIL region from the β1-adrenergic receptor. We observed that TIL recruits endophilin to membranes composed of 95 mol% of zwitterionic lipids via the SH3 domain. More importantly, endophilin recruited via TIL tubulates vesicles and gets sorted onto highly curved membrane tubules. These observations indicate that the cellular membrane bending and curvature sensing activities of endophilin can be facilitated through detection of the TIL of activated GPCRs in addition to binding to anionic lipids. Furthermore, we show that TIL electrostatically interacts with membranes composed of anionic lipids. Therefore, anionic lipids can modulate TIL/SH3 domain binding. Overall, our findings imply that an interplay between TIL, charged membrane lipids, BAR domain, and SH3 domain could exist in the biological system and that these components may act in coordination to regulate the internalization of cellular receptors.
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Affiliation(s)
- Samsuzzoha Mondal
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Karthik B Narayan
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Imania Powers
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Samuel Botterbusch
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Tobias Baumgart
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
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Heckert JM, Kipnis ST, Kumar S, Botterbusch S, Alderson A, Bennett B, Creamer C, Eads JR, Soulen MC, Pryma DA, Mankoff DA, Metz DC, Katona BW. Abnormal Pretreatment Liver Function Tests Are Associated with Discontinuation of Peptide Receptor Radionuclide Therapy in a U.S.-Based Neuroendocrine Tumor Cohort. Oncologist 2020; 25:572-578. [PMID: 32141667 DOI: 10.1634/theoncologist.2019-0743] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Accepted: 02/05/2020] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Peptide receptor radionuclide therapy (PRRT) is effective for treating midgut neuroendocrine tumors (NETs); however, incorporation of PRRT into routine practice in the U.S. is not well studied. Herein we analyze the first year of PRRT implementation to determine tolerance of PRRT and factors that increase risk of PRRT discontinuation. MATERIALS AND METHODS Medical records were reviewed and data were abstracted on all patients with NETs scheduled for PRRT during the first year of PRRT implementation at a U.S. NET referral center (August 2018 through July 2019). Logistic regression was used to identify factors associated with PRRT discontinuation. RESULTS Fifty-five patients (56% male) were scheduled for PRRT over the study period. The most common primary NET location was small bowel (47%), followed by pancreas (26%), and 84% of the NETs were World Health Organization grade 1 or 2. The cohort was heavily pretreated with somatostatin analog (SSA) therapy (98%), non-SSA systemic therapy (64%), primary tumor resection (73%), and liver-directed therapy (55%). At the time of analysis, 52 patients completed at least one PRRT treatment. Toxicities including bone marrow suppression and liver function test (LFT) abnormalities were comparable to prior publications. Eleven patients (21%) prematurely discontinued PRRT because of toxicity or an adverse event. Pretreatment LFT abnormality was associated with increased risk of PRRT cancellation (odds ratio: 12; 95% confidence interval: 2.59-55.54; p < .001). CONCLUSION PRRT can be administered to a diverse NET population at a U.S. NET referral center. Baseline liver function test abnormality increases the likelihood of PRRT discontinuation. IMPLICATIONS FOR PRACTICE Peptide receptor radionuclide therapy (PRRT) can be successfully implemented at a U.S. neuroendocrine tumor (NET) referral center in a NET population that is diverse in tumor location, grade, and prior treatment history. Toxicity and adverse effects of PRRT are comparable to prior reports; however, 21% of individuals prematurely discontinued PRRT. Patients with baseline liver function test abnormalities were more likely to discontinue PRRT than patients with normal liver function tests, which should be taken into consideration when selecting treatment options for NETs.
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Affiliation(s)
- Jason M Heckert
- Division of Internal Medicine, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Sarit T Kipnis
- Division of Internal Medicine, Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Shria Kumar
- Division of Gastroenterology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Samuel Botterbusch
- Division of Gastroenterology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Alice Alderson
- Division of Gastroenterology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Bonita Bennett
- Division of Gastroenterology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Caroline Creamer
- Division of Gastroenterology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Jennifer R Eads
- Division of Hematology and Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Michael C Soulen
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Daniel A Pryma
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - David A Mankoff
- Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - David C Metz
- Division of Gastroenterology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Bryson W Katona
- Division of Gastroenterology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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