Structural Requirements for Major Histocompatibility Complex Class II Invariant Chain Endocytosis and Lysosomal Targeting

Abstract

The invariant chain (Ii) targets newly synthesized major histocompatibility complex class II complexes to a lysosome-like compartment. Previously, we demonstrated that both the cytoplasmic tail (CT) and transmembrane (TM) domains of Ii were sufficient for this targeting and that the CT contains two di-leucine signals, 3

Down-Regulation of Cell Surface Receptors Is Modulated by Polar Residues within the Transmembrane Domain

“…Thus, the half-life of a protein at the cell surface becomes (Kang et al, 1998). All other portions of this chimera are derived from the wild-type TR (unshaded areas).…”

“…The rate of Tf internalization was determined with the internal surface (IN/SUR) method (Wiley and Cunningham, 1982) as described previously (Kang et al, 1998). For the proteolysis assay, CEFs expressing the various TR and Ii-TR constructs were plated in triplicate at a density of 7.5ϫ10 4 cells/cm 2 , in 24-well tissue culture plates 24 h before the assay (Costar, Cambridge, MA).…”

“…The Ii TM 11-19 mutant was originally described in Kang et al (1998). The oligonucleotide primer for preparation of the Ii TM 11-19 mutant was GGGACTATTGC-CCTGCTCCTCGCTGGCGCGGCCGCCTTTATGATTGGC, and the primer for the TR TM Thr 11 Gln 17 Thr 19 mutant was GGGACTAT-TACTGTGATCGTCTTTTTCCAGATTACATTTATGATTGGC.…”

“…After incubation, the medium was collected, protein was precipitated in 10% trichloroacetic acid (TCA) and removed by centrifugation, and the acid-soluble and acid-insoluble radioactivity was counted in a gamma counter. The surface-bound and internalized Tf in CEFs was determined by the acid wash procedure described in Kang et al (1998).…”

“…Perhaps the clearest example of this is the epidermal growth factor receptor that requires an active cytoplasmic kinase domain for entry into internal vesicles of the multivesicular body (Futter et al, 1993). Other late endosomal/lysosomal targeting signals have been identified in the cytoplasmic tails of P-selectin (Green et al, 1994), the mannose-6-phosphate receptor (Johnson and Kornfeld, 1992a,b), the major histocompatibility complex (MHC) class II invariant chain (Ii) (Bakke and Dobberstein, 1990;Pieters et al, 1993;Bremnes et al, 1994;Odorizzi et al, 1994;Pond et al, 1995;Kang et al, 1998), the T cell receptor CD3 ␥-chain (Letourneur and Klausner, 1992), lysosomal acid phosphatase (Peters et al, 1990), and lysosome-associated membrane glycoprotein (Williams and Fukuda, 1990), suggesting that entry into multivesicular bodies does not occur by default.…”