Edwin Krebs (1918-2009), A Great Pioneer in Kinase Research

Those who have ever studied the reversible phosphorylation of proteins would
owe much both Edwin Krebs and his colleague Edmond Fischer at University
of Washington in Seattle. In 1950s they found the first protein kinase,
phosphorylase kinase (PK), which phosphorylates and activates the enzyme
glycogen phosphorylase (GP). This phosphorylase catalyzes the hydrolysis
of glycogen, supplying the glucose essential for a variety of our actions
such as muscle contraction and learning. PK also requires the phosphorylation
by another kinase called PKA (cyclic AMP-dependent kinase). cyclic AMP (cAMP)
is a second messenger that is produced by adenylate cyclase (AC) from ATP.
AC is activated by a GTPase (or G protein) called Gs. Thus,
A G protein activates this kinase cascade through the second messenger cAMP.

A similar G protein-kinase cascade was found around 1994, when Ed Manser
in Singapore cloned the first mammalian member of PAK family (PAK1) in brain.
This kinase (PAK1) is directly activated by another G protein family (RAC
and CDC42).
Later it was found that RAC/CDC42 is down stream of another kinase (PI-3
kinase) which is directly activated by the oncogenic G protein RAS. In
other words PAK1
mediates the oncogenic signal of RAS, and is essential for the growth of
more than 70% of all human cancers including breast and prostate cancers
and NF (neurofibromatosis) tumors. In addition, PAK1 is essential for both
metastasis and angiogenesis of these solid tumors. Since PAK1 is not essential
for the normal cell growth, anti-PAK1 drugs such as Bio 30 (NZ propolis
extract) would be powerful therapeutics for the treatment of these PAK1-dependent
cancers and NF without any side effect. Thus, cancer and NF patients should
greatly appreciate the discovery of the first kinase cascade (PKA-PK-GP)
during 1950s-1960s, which eventually led to the discovery of the oncogenic
RAS-PI-3 kinase-RAC/CDC42-PAK1 signal cascade in 1990s.

Accordingly, the 1992 Nobel prize in Physiology/Medicine was awarded to
Edwin Krebs and Edmond Fischer.