Cellular concentrations of Protein Kinase D1 in HEK293T and INS-1 cells

Protein kinase D1 (PRKD1, also referred to as PKD1), has been proposed to undergo concentration dependent dimerization in vitro. To test whether the cellular concentration of PKD1 is in the range of the dissociation constant obtained, the expression level of PKD1 was investigated by PRM. To this end, an equimolar mixture of pure, recombinant protein comprising the PKD N-terminus (residues 48-198) and C-terminus (residues 395-892) was used to spike the cell lysates of human HEK293T cells or the rat cell line INS-1. In the latter case, only peptides that are identical between the human and rat PKD1 protein were used to estimate the cellular expression level of PKD1.