The first step in growth factor pathway activation is

A. Ras activation

B. receptor phosphorlyation

C. receptor dimerizaton

D. Binding of SH2-containing protiens.

The correct option is C. receptor dimerizaton.

Explanation:

Growth Factors are protein substances found in our blood and play an important role in intercellular communication. These protein substances bind to receptors on the surface of the cell, with the main result of the activation of cell proliferation and / or differentiation. Many growth factors are very versatile, stimulating cell division in numerous different cell types, while others are specific to a particular cell type.

For the activation of a growth factor, dimerization or oligomerization of the receptor is necessary for kinase activity to occur, triggering intracellular signaling cascades. The dimerization can be between two identical receptors (homodimerization) or between different members of the same family (heterodimerization). The dimerization of the receptor, leads to the activation of its tyrosine kinase and the transphosphorylation of the tyrosine residues, releasing a signal transduction into the cell.