title: The α-helical content of the transmembrane domain of the British dementia protein-2 (Bri2) determines its processing by signal peptide peptidase-like 2b (SPPL2b).
abstract: Regulated intramembrane proteolysis is a widely accepted concept describing the processing of various transmembrane proteins via ectodomain shedding followed by an intramembrane cleavage. The resulting cleavage products can be involved in reverse signaling. Presenilins, which constitute the active center of the γ-secretase complex, signal peptide peptidase (SPP), and its homologues, the SPP-like (SPPL) proteases are members of the family of intramembrane-cleaving aspartyl proteases of the GXGD-type. We recently demonstrated that Bri2 (itm2b) is a substrate for regulated intramembrane proteolysis by SPPL2a and SPPL2b. Intramembrane cleavage of Bri2 is triggered by an initial shedding event catalyzed by A Disintegrin and Metalloprotease 10 (ADAM10). Additionally primary sequence determinants within the intracellular domain, the transmembrane domain and the luminal juxtamembrane domain are required for efficient cleavage of Bri2 by SPPL2b. Using mutagenesis and circular dichroism spectroscopy we now demonstrate that a high α-helical content of the Bri2 transmembrane domain (TMD) reduces cleavage efficiency of Bri2 by SPPL2b, while the presence of a GXXXG dimerization motif influences the intramembrane cleavage only to a minor extent. Surprisingly, only one of the four conserved intramembrane glycine residues significantly affects the secondary structure of the Bri2 TMD and thereby its intramembrane cleavage. Other glycine residues do not influence the α-helical content of the transmembrane domain nor its intramembrane processing.
authors.affiliation: Adolf Butenandt Institute, Biochemistry, Ludwig-Maximilians University Munich, 80336 Munich, Germany.
authors.forename: Regina
authors.initials: R
authors.lastname: Fluhrer
authors.forename: Lucas
authors.initials: L
authors.lastname: Martin
authors.forename: Bärbel
authors.initials: B
authors.lastname: Klier
authors.forename: Martina
authors.initials: M
authors.lastname: Haug-Kröper
authors.forename: Gudula
authors.initials: G
authors.lastname: Grammer
authors.forename: Brigitte
authors.initials: B
authors.lastname: Nuscher
authors.forename: Christian
authors.initials: C
authors.lastname: Haass
mesh_terms: D051722:ADAM Proteins / Q000235:genetics / Q000378:metabolism; D000072197:ADAM10 Protein; D048868:Adaptor Proteins, Signal Transducing; D020816:Amino Acid Motifs; D053829:Amyloid Precursor Protein Secretases / Q000235:genetics / Q000378:metabolism; D016282:Aspartic Acid Endopeptidases / Q000235:genetics / Q000378:metabolism*; D002942:Circular Dichroism / Q000379:methods; D057809:HEK293 Cells; D006801:Humans; D008562:Membrane Glycoproteins; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D016296:Mutagenesis; D017434:Protein Structure, Tertiary; D059748:Proteolysis
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C120083:ITM2B protein, human; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D053829:Amyloid Precursor Protein Secretases; D016282:Aspartic Acid Endopeptidases; C526456:SPPL2b protein, human; D051722:ADAM Proteins; D000072197:ADAM10 Protein; C491236:ADAM10 protein, human