title: Bleeding due to disruption of a cargo-specific ER-to-Golgi transport complex.
abstract: Mutations in LMAN1 (also called ERGIC-53) result in combined deficiency of factor V and factor VIII (F5F8D), an autosomal recessive bleeding disorder characterized by coordinate reduction of both clotting proteins. LMAN1 is a mannose-binding type 1 transmembrane protein localized to the endoplasmic reticulum-Golgi intermediate compartment (ERGIC; refs. 2,3), suggesting that F5F8D could result from a defect in secretion of factor V and factor VIII (ref. 4). Correctly folded proteins destined for secretion are packaged in the ER into COPII-coated vesicles, which subsequently fuse to form the ERGIC. Secretion of certain abundant proteins suggests a default pathway requiring no export signals (bulk flow; refs. 6,7). An alternative mechanism involves selective packaging of secreted proteins with the help of specific cargo receptors. The latter model would be consistent with mutations in LMAN1 causing a selective block to export of factor V and factor VIII. But approximately 30% of individuals with F5F8D have normal levels of LMAN1, suggesting that mutations in another gene may also be associated with F5F8D. Here we show that inactivating mutations in MCFD2 cause F5F8D with a phenotype indistinguishable from that caused by mutations in LMAN1. MCFD2 is localized to the ERGIC through a direct, calcium-dependent interaction with LMAN1. These findings suggest that the MCFD2-LMAN1 complex forms a specific cargo receptor for the ER-to-Golgi transport of selected proteins.
authors.affiliation: Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan 48109-0650, USA.
authors.forename: Bin
authors.initials: B
authors.lastname: Zhang
authors.forename: Michael A
authors.initials: MA
authors.lastname: Cunningham
authors.forename: William C
authors.initials: WC
authors.lastname: Nichols
authors.forename: John A
authors.initials: JA
authors.lastname: Bernat
authors.forename: Uri
authors.initials: U
authors.lastname: Seligsohn
authors.forename: Steven W
authors.initials: SW
authors.lastname: Pipe
authors.forename: John H
authors.initials: JH
authors.lastname: McVey
authors.forename: Ursula
authors.initials: U
authors.lastname: Schulte-Overberg
authors.forename: Norma B
authors.initials: NB
authors.lastname: de Bosch
authors.forename: Arlette
authors.initials: A
authors.lastname: Ruiz-Saez
authors.forename: Gilbert C
authors.initials: GC
authors.lastname: White
authors.forename: E G D
authors.initials: EG
authors.lastname: Tuddenham
authors.forename: Randal J
authors.initials: RJ
authors.lastname: Kaufman
authors.forename: David
authors.initials: D
authors.lastname: Ginsburg
mesh_terms: D000595:Amino Acid Sequence; D001693:Biological Transport, Active / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005166:Factor V Deficiency / Q000235:genetics* / Q000378:metabolism; D005260:Female; D006056:Golgi Apparatus / Q000378:metabolism; D006367:HeLa Cells; D006467:Hemophilia A / Q000235:genetics* / Q000378:metabolism; D006470:Hemorrhage / Q000209:etiology / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008297:Male; D037241:Mannose-Binding Lectins / Q000235:genetics*; D008565:Membrane Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D010375:Pedigree; D017386:Sequence Homology, Amino Acid; D014162:Transfection; D033921:Vesicular Transport Proteins
chemical_list: D002352:Carrier Proteins; C084004:LMAN1 protein, human; C475146:MCFD2 protein, human; D037241:Mannose-Binding Lectins; D008565:Membrane Proteins; D033921:Vesicular Transport Proteins