#Question id: 1387

The ability of a population of fibroblasts to migrate along the surface of a tissue culture dish depends on adhesion between the cell surface and the extracellular matrix molecules coating the dish. The dish is coated with laminin, and the only cell-surface protein capable of binding laminin is a cell-adhesion protein called an integrin. Integrins are integral plasma-membrane proteins that function as heterodimers. Under these conditions the rate at which a fibroblast can migrate along the laminin coated culture dish is proportional to the strength of adhesion between the cell and the laminin substrate. The table below lists the rate of cell migration observed for fibroblasts genetically engineered to generate the indicated phenotypes. Microinjection into the cytoplasm of a wild. type cell of a solution of a synthetic peptide possessing the same sequence as the integrin beta subunit cytoplasmic domain would be expected to yield an average fibroblast-cell migration rat

Fibroblast Phenotype	Level of Integrin Heterodimer at the Cell Surface (percent of wild type)	Rate of Cell Migration (pm/min)
1. Wild type	100	2
2. Overexpression of the wild-type integrin alpha subunit	104	2
3. Overexpression of an integrin beta subunit lacking the cytoplasmic domain	96	0.6
4. Overexpression of the soluble cytoplasmic domain of an integrin beta subunit	98	0.6
5. Absence of the integrin alpha subunit	Less than 1	0.05