Mitogen activated protein kinase at the nuclear pore complex.

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Mitogen activated protein (MAP) kinases regulate eukaryotic cell proliferation.
• Nuclear pore complex (NPC) controls nucleocytoplasmic traffic, influencing gene expression, cell growth, viability, and homeostasis.
• MAP kinases may associate with the NPC to modulate nuclear transport.

Purpose of the Study:

• To investigate kinase activity and presence within isolated nuclear pore complex (NPC) fractions.
• To identify specific kinases associated with the NPC and their substrates.
• To explore the role of MAP kinases in NPC function and regulation.

Main Methods:

• Isolation of highly enriched nuclear pore complex (NPC) fractions.
• Assay for endogenous kinase activity within NPC fractions.
• Phosphorylation analysis of a 30 kD nuclear pore protein (Nup30).
• Inhibition studies using MAP kinase antagonists (apigenin, PD-98059) and a p38 inhibitor (SB-202190).
• High-throughput profiling of enriched NPCs for MAP kinase family members.

Main Results:

• Endogenous kinase activity was detected within the NPC fraction.
• A 30 kD nuclear pore protein (Nup30) was identified as a substrate for NPC-associated kinases.
• Phosphorylation of Nup30 was inhibited by MAP kinase antagonists and a p38 inhibitor.
• All members of the MAP kinase family, including extracellular signal-regulated kinases (ERK), p38, and c-Jun N-terminal kinase (JNK), were constitutively present in enriched NPCs.

Conclusions:

• The nuclear pore complex (NPC) harbors associated MAP kinases, including ERK and p38.
• These associated MAP kinases play a role in regulating nuclear pore function.
• Phosphorylation of Nup30 by MAP kinases suggests a mechanism for controlling nucleocytoplasmic transport and cellular processes.