Premium
β1B integrin subunit contains a double lysine motif that can cause accumulation within the endoplasmic reticulum
Author(s) -
Kee Wai Jing,
Li Elizabeth R.,
Watt Fiona M.
Publication year - 2000
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/(sici)1097-4644(20000701)78:1<97::aid-jcb9>3.0.co;2-5
Subject(s) - endoplasmic reticulum , cytoplasm , microbiology and biotechnology , integrin , biology , transfection , stim1 , cell , cell culture , biochemistry , genetics
Human epidermal keratinocytes are one of the few cell types that express the β1B splice variant of the β1 integrin subunit. Although in transfection experiments β1B acts as a dominant negative inhibitor of cell adhesion, we found that β1B was expressed at very low levels in keratinocytes, both in vivo and in culture, and had a predominantly cytoplasmic distribution, concentrated within the endoplasmic reticulum. To examine why β1B accumulated in the cytoplasm, we prepared chimeras between CD8α and the β1A and β1B integrin cytoplasmic domains. In transfected HeLa cells, both constructs reached the cell surface but the rate of maturation of the β1B chimera was considerably retarded relative to β1A. The β1B cytoplasmic domain contains two lysine residues that resemble the double lysine motif characteristic of many proteins that are resident within the endoplasmic reticulum. Mutation of each lysine individually to serine had no effect on CD8β1B maturation, but when both residues were mutated the rate of CD8β1B maturation increased to that of CD8β1A. Further analysis of β1B function in keratinocytes must, therefore, take into account the low abundance of the isoform relative to β1A and the potential for β1B to accumulate in the endoplasmic reticulum. J. Cell. Biochem. 78:97–111, 2000. © 2000 Wiley‐Liss, Inc.