Fes/ Fps Gene

Fes: Feline Sarcoma

• Same as Fps: Fujinami poultry sarcoma• A proto-oncogene• Located in the cytoplasm• Encodes a non-receptor protein-tyrosine

kinase• Fes/Fps and Fer (Fes-related protein) are the

only members of a distinct family of kinases

Predicted Domains

• Amino-terminal FCH domain

• Three Coiled-coil domains

• Central SH2 domain

• Carboxy-terminal kinase domain

FCH Domain

• Unknown structure and function• Apparent affinity for microtubules• Functions of homologous FCH regions in other

proteins, such as regulation of cytoskeletal rearrangements, vesicular transport, and endocytosis, could provide insight to its function

Three Coiled-Coil Domains

• Coiled-Coil – Quaternary protein structure formed by two or three helices interacting with each other along their length

• Negative regulation of kinase activity• Mediate oligomerization (see diagram)• Recruitment of signaling partners

Hypothetical means of regulating oligomerization: Smithgall et al. 1998

Central SH2 Domain

• Mediates protein-protein interactions that are essential for the transforming activities of the oncogenic Fps/Fes kinase (Greer 2002)

• Possible SH2 domain-interacting proteins:BcrAbl (Kinase)FAK (Focal Adhesion Kinase)

Carboxy-terminus Kinase Domain

• Phosphorylates target proteins• Possible target proteins:

Bcr

Abl

FAK

Mutations in Coiled-Coil Domains

Experiment: Cheng et al. 2001• Mutants expressed in myeloid-leukemia cell lines• One bp deletion in first c-c domain: dramatic

increase in kinase activity• Cells were less dependent on growth stimulus and

spreading was induced

Mutations in Coiled-Coil Domains

Experiment: Cheng et al. 2001• One bp mutation in the second c-c domain had no

effect

BUT:• Double-mutant led to reduced kinase activity

Mutation – Protein Fusion

Peter Greer 2002

Participation in Signal Transduction Pathways

• Fes/ Fps is thought to act downstream of cytokine receptors

• Functions of these pathways are unknown

Fes/ Fps is thought to play a role in regulating…

• Cell-matrix and cell-cell adhesions

• Hematopoiesis (controversial)

• Cytoskeletal rearrangements

• Intracellular signaling

• *Bcr-Abl

Fes and Bcr-Abl

• Hematopoietic cells need cytokines in order to survive and grow

• Bcr-Abl is an oncogene whose expression makes hematopoietic cells grow independently of cytokines

• Fes expression in leukemia cells antagonizes the actions of Bcr-Abl

.: one normal function of the Fes gene is to suppress a rare oncogene

Lionberger and Smithgall 2000

Review:

• Fes acts downstream of cytokine receptors

• Hematopoietic cells need cytokines in order to survive and grow

• What will happen when the Fes gene is eliminated from an animal?

Hypothesis:

A mouse lacking both copies of the Fes gene will not survive since hematopoiesis will not

function properly.

Results:• Fes-null mice were healthy and viable!

• Two small problems:

1) the mice had slightly less bone marrow progenitors and circulating mature myeloid cells

2) the mice were more sensitive to Lipopolysaccharide (LPS) (~bacteria)

• Proof: the Fes-null phenotypes were rescued using a wild-type Fes transgene

Zirngibl et al. 2002

Conclusion:

• Fes is not essential for development and survival

• The roles of Fes and Fer may be redundant

.:What will happen when to a mouse that lacks both the Fes and Fer genes?