Signal-peptide-peptidase-like 2a is required for CD74 intramembrane proteolysis in human B cells

TY - JOUR

T1 - Signal-peptide-peptidase-like 2a is required for CD74 intramembrane proteolysis in human B cells

AU - Schneppenheim, Janna

AU - Hüttl, Susann

AU - Kruchen, Anne

AU - Fluhrer, Regina

AU - Müller, Ingo

AU - Saftig, Paul

AU - Schneppenheim, Reinhard

AU - Martin, Christa L

AU - Schröder, Bernd

N1 - Copyright © 2014 Elsevier Inc. All rights reserved.

PY - 2014/8/15

Y1 - 2014/8/15

N2 - The invariant chain (CD74) mediates targeting of the MHCII complex to endosomal compartments, where CD74 undergoes degradation allowing MHCII to acquire peptides. We demonstrated recently that intramembrane proteolysis of the final membrane-bound N-terminal fragment (NTF) of CD74 is catalyzed by Signal-peptide-peptidase-like 2a (SPPL2a) and that this process is indispensable for development and function of B lymphocytes in mice. In SPPL2a(-/-) mice, homeostasis of these cells is disturbed by the accumulation of the unprocessed CD74 NTF. So far, evidence for this essential role of SPPL2a is restricted to mice. Nevertheless, inhibition of SPPL2a has been suggested as novel approach to target B cells for treating autoimmunity. Here, we characterize human B cell lines with a homozygous microdeletion on chromosome 15. We demonstrate that this deletion disrupts the SPPL2a genomic locus and leads to loss of SPPL2a transcript. Lymphoblastoid cell lines from patients with this deletion exhibit absence of SPPL2a at the protein level and show an accumulation of the CD74 NTF comparable to B cells from SPPL2a(-/-) mice. By this means, we present evidence that the role of SPPL2a in CD74 proteolysis is conserved in human B cells and provide support for modulation of SPPL2a activity as a therapeutic concept.

AB - The invariant chain (CD74) mediates targeting of the MHCII complex to endosomal compartments, where CD74 undergoes degradation allowing MHCII to acquire peptides. We demonstrated recently that intramembrane proteolysis of the final membrane-bound N-terminal fragment (NTF) of CD74 is catalyzed by Signal-peptide-peptidase-like 2a (SPPL2a) and that this process is indispensable for development and function of B lymphocytes in mice. In SPPL2a(-/-) mice, homeostasis of these cells is disturbed by the accumulation of the unprocessed CD74 NTF. So far, evidence for this essential role of SPPL2a is restricted to mice. Nevertheless, inhibition of SPPL2a has been suggested as novel approach to target B cells for treating autoimmunity. Here, we characterize human B cell lines with a homozygous microdeletion on chromosome 15. We demonstrate that this deletion disrupts the SPPL2a genomic locus and leads to loss of SPPL2a transcript. Lymphoblastoid cell lines from patients with this deletion exhibit absence of SPPL2a at the protein level and show an accumulation of the CD74 NTF comparable to B cells from SPPL2a(-/-) mice. By this means, we present evidence that the role of SPPL2a in CD74 proteolysis is conserved in human B cells and provide support for modulation of SPPL2a activity as a therapeutic concept.

KW - Antigens, Differentiation, B-Lymphocyte

KW - Aspartic Acid Endopeptidases

KW - B-Lymphocytes

KW - Cell Line

KW - Chromosome Deletion

KW - Chromosomes, Human, Pair 15

KW - Histocompatibility Antigens Class II

KW - Homozygote

KW - Humans

KW - Immunologic Deficiency Syndromes

KW - Intracellular Membranes

KW - Peptide Fragments

U2 - 10.1016/j.bbrc.2014.07.051

DO - 10.1016/j.bbrc.2014.07.051

M3 - SCORING: Journal article

C2 - 25035924

VL - 451

SP - 48

EP - 53

JO - BIOCHEM BIOPH RES CO

JF - BIOCHEM BIOPH RES CO

SN - 0006-291X

IS - 1

ER -