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beta1B integrin subunit contains a double lysine motif that can cause accumulation within the endoplasmic reticulum

W J Kee1, E R Li, F M Watt

  • 1Keratinocyte Laboratory, Imperial Cancer Research Fund, London, WC2A 3PX, United Kingdom.

Journal of Cellular Biochemistry
|May 8, 2000
PubMed

Insights

The beta1B integrin subunit is poorly expressed in human keratinocytes and primarily accumulates in the endoplasmic reticulum. This retention is due to specific lysine residues, impacting its cellular function and cell adhesion.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Human epidermal keratinocytes uniquely express the beta1B splice variant of the beta1 integrin subunit.
  • In vitro studies suggest beta1B inhibits cell adhesion, but its low expression in keratinocytes warrants further investigation.

Purpose of the Study:

  • To investigate the reasons behind the low expression and cytoplasmic accumulation of beta1B integrin in keratinocytes.
  • To elucidate the role of specific cytoplasmic domain residues in beta1B trafficking and maturation.

Main Methods:

  • Constructed chimeric proteins linking CD8alpha to beta1A and beta1B integrin cytoplasmic domains.
  • Utilized transfected HeLa cells to analyze the maturation and cell surface expression of these chimeras.
  • Employed site-directed mutagenesis to alter specific lysine residues within the beta1B cytoplasmic domain.

Main Results:

  • Beta1B integrin chimeras exhibited significantly retarded maturation compared to beta1A counterparts.
  • The beta1B cytoplasmic domain contains a double lysine motif, characteristic of endoplasmic reticulum-resident proteins.
  • Mutating both lysine residues to serine restored maturation rates to levels comparable to beta1A.

Conclusions:

  • The low abundance and endoplasmic reticulum retention of beta1B integrin in keratinocytes are influenced by its cytoplasmic domain.
  • Specific lysine residues within the beta1B cytoplasmic domain mediate its retention in the endoplasmic reticulum, affecting its functional availability.
  • Future studies on beta1B function in keratinocytes should consider its limited expression and intracellular localization.

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