Contrasting roles for integrin beta 1 and beta 5 cytoplasmic domains in subcellular localization, cell proliferation, and cell migration.
To carry out a detailed comparison of the roles of integrin beta 1 and beta 5 cytoplasmic domains, we expressed both wild type beta 1 and chimeric beta 1/5 constructs in CHO cells. In the latter, the cytoplasmic domain of beta 1 was replaced with that of beta 5. The human beta 1 and beta 1/5 constructs appeared at similar levels at the cell surface (mostly as alpha 5 beta 1 heterodimers) and contributed equally to CHO cell adhesion to fibronectin. However, beta 1 but not beta 1/5 localized to focal adhesion-like structures when CHO cells were spread on fibronectin. Furthermore, only the beta 1-CHO cells showed increased proliferation in response to fibronectin plus an integrin-activating anti-beta 1 antibody, and showed increased appearance of 32P-labeled protein (p90) that correlated with proliferation. In sharp contrast, the beta 1/5-CHO cells were notably more migratory than beta 1-CHO cells in a transwell haptotactic migration assay. These results indicate that the beta 1 and beta 5 integrin subunit cytoplasmic domains can translate similar adhesive information into highly contrasting subsequent events. Thus, we have established that "inside-out" and "outside-in" integrin signaling pathways are regulated by fundamentally distinct mechanisms. In addition, we suggest that the same properties of the beta 1 cytoplasmic domain that promote recruitment to visible focal adhesion-like structures may also be conductive to cell proliferation. Conversely, the properties of the beta 5 tail that make it less likely to localize into focal adhesion-like structures may contribute to enhanced cell migration.
Pasqualini
R
R
Dana-Farber Cancer Institute, Boston, Massachusetts 02115.
Hemler
M E
ME
D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D002448:Cell Adhesion / Q000502:physiology; D002455:Cell Division / Q000502:physiology; D002465:Cell Movement / Q000502:physiology; D003001:Cloning, Molecular; D006224:Cricetinae; D003593:Cytoplasm / Q000502:physiology; D005353:Fibronectins; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D039641:Integrin beta Chains; D019012:Integrin beta1; D016023:Integrins / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000502:physiology
D005353:Fibronectins; D039641:Integrin beta Chains; D019012:Integrin beta1; D016023:Integrins; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; C084344:integrin beta5