title: Filamin A is reduced and contributes to the CASR sensitivity in human parathyroid tumors.
abstract: Parathyroid tumors display reduced sensitivity to extracellular calcium ([Ca2+]o). [Ca2+]oactivates calcium-sensing receptor (CASR), which interacts with the scaffold protein filamin A (FLNA). The study aimed to investigate: (1) the FLNA expression in human parathyroid tumors, (2) its effects on the CASR mRNA and protein expression, and (3) on ERK signaling activation, (4) the effect of the carboxy-terminal CASR variants and (5) of the treatment with the CASR agonist R568 on FLNA-mediated ERK phosphorylation in HEK293 cells. Full-length FLNA immunostaining was variably reduced in parathyroid tumors. Immunofluorescence showed that FLNA localized in membrane and cytoplasm and co-localized with CASR in parathyroid adenomas (PAds)-derived cells. Cleaved C-terminus FLNA fragment could also be detected in PAds nuclear protein fractions. In HEK293 cells transfected with 990R-CASR or 990G-CASR variants, silencing of endogenous FLNA reduced CASR mRNA levels and total and membrane-associated CASR proteins. In agreement, FLNA mRNA levels positively correlated with CASR expression in a series of 74 PAds; however, any significant correlation with primary hyperparathyroidism severity could be detected and FLNA transcript levels did not differ between PAds harboring 990R or 990G CASR variants. R568 treatment was efficient in restoring 990R-CASR and 990G-CASR sensitivity to [Ca2+]oin the absence of FLNA. In conclusion, FLNA is downregulated in parathyroid tumors and parallels the CASR expression levels. Loss of FLNA reduces CASR mRNA and protein expression levels and the CASR-induced ERK phosphorylation. FLNA is involved in receptor expression, membrane localization and ERK signaling activation of both 990R and 990G CASR variants.
authors.affiliation: Department of Health SciencesUniversity of Milan, Milan, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Mingione
authors.affiliation: Laboratory of Experimental EndocrinologyIRCCS Istituto Ortopedico Galeazzi, Milan, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Verdelli
authors.affiliation: Division of PathologyDepartment of Biomedical, Surgical and Dental Sciences, University of Milan, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Ferrero
authors.affiliation: Division of PathologyDepartment of Pathophysiology and Transplantation, University of Milan, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico and Istituto Nazionale Genetica Molecolare (INGM) Romeo ed Enrica Invernizzi, Milan, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Vaira
authors.affiliation: Medical GeneticsIRCCS Hospital Casa Sollievo della Sofferenza, San Giovanni Rotondo (FG), Italy.
authors.forename: Vito
authors.initials: V
authors.lastname: Guarnieri
authors.affiliation: Endocrine UnitIRCCS Hospital Casa Sollievo della Sofferenza, San Giovanni Rotondo (FG), Italy.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Scillitani
authors.affiliation: Endocrine SurgeryIRCCS Fondazione Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Vicentini
authors.affiliation: Internal Medicine UnitA.O. Alessandro Manzoni, Lecco, Italy.
authors.forename: Gianni
authors.initials: G
authors.lastname: Balza
authors.affiliation: Endocrine SurgeryIRCCS Ospedale San Raffaele, Milan, Italy.
authors.forename: Edoardo
authors.initials: E
authors.lastname: Beretta
authors.affiliation: Sidra Medical and Research CenterDoha, Qatar.
authors.forename: Annalisa
authors.initials: A
authors.lastname: Terranegra
authors.affiliation: Nephrology and Dialysis UnitIRCCS Ospedale San Raffaele, Milan, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Vezzoli
authors.affiliation: Department of Health SciencesUniversity of Milan, Milan, Italy laura.soldati@unimi.it sabrina.corbetta@unimi.it.
authors.forename: Laura
authors.initials: L
authors.lastname: Soldati
authors.affiliation: Endocrinology ServiceDepartment of Biomedical Sciences for Health, University of Milan, IRCCS Istituto Ortopedico Galeazzi, Milan, Italy laura.soldati@unimi.it sabrina.corbetta@unimi.it.
authors.forename: Sabrina
authors.initials: S
authors.lastname: Corbetta
mesh_terms: D000368:Aged; D000483:Alleles; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D064448:Filamins / Q000235:genetics* / Q000378:metabolism*; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic; D020868:Gene Silencing; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D009154:Mutation; D010280:Parathyroid Glands / Q000378:metabolism; D010282:Parathyroid Neoplasms / Q000097:blood / Q000209:etiology* / Q000378:metabolism*; D010766:Phosphorylation; D012333:RNA, Messenger / Q000235:genetics; D044169:Receptors, Calcium-Sensing / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D064448:Filamins; D012333:RNA, Messenger; D044169:Receptors, Calcium-Sensing; D048049:Extracellular Signal-Regulated MAP Kinases
keywords: calcium-sensing receptor; filamin A; parathyroid tumors; primary hyperparathyroidism