Mutational analysis of cell cycle inhibition by integrin beta1C

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Integrin beta1C is an alternatively spliced variant of the beta1 integrin subunit.
• It is known to inhibit cell cycle progression.

Purpose of the Study:

• To analyze the requirements for growth suppression mediated by integrin beta1C.
• To identify the specific domains within beta1C responsible for its inhibitory function.

Main Methods:

• Construction and expression of chimeric proteins involving the Tac subunit and various integrin beta cytoplasmic domains.
• Expression of soluble green fluorescent protein (GFP) fusion proteins containing specific beta1C domains.
• Analysis of growth inhibition in mouse 10T1/2 cells, human endothelial cells (EV304), and prostate cancer cells (DU145).

Main Results:

• A chimera with the beta1C cytoplasmic domain (732-805) strongly inhibited cell growth, unlike chimeras with other beta1 or beta3/5 cytoplasmic domains.
• The beta1C-specific domain (758-805) was sufficient for growth inhibition, functioning even as a soluble protein without membrane targeting.
• An 18-amino acid sequence (775-792) within the beta1C-specific domain was necessary and sufficient for maximal growth inhibition.

Conclusions:

• Growth inhibition by integrin beta1C does not require the intact integrin receptor or membrane localization.
• The unique C-terminal domain of beta1C, particularly residues 775-792, is critical for its function as a potent cell growth inhibitor.
• Integrin beta1C has a role as a tumor suppressor in endothelial and prostate epithelial cells.