The c-Jun amino-terminal kinases (JNKs) /stress-activated protein kinases (SAPKs) play a crucial role in stress responses in mammalian cells. The mechanism underlying this pathway in the hematopoietic system is unclear, but it is a key in understanding the molecular basis of blood cell differentiation. We have cloned a novel protein kinase, termed hematopoietic progenitor kinase 1 (HPK1), that is expressed predominantly in hematopoietic cells, including early progenitor cells. HPK1 is related distantly to the p21 (Cdc42/Rac1) activated kinase (PAK) and yeast STE20 implicated in the mitogen-activated protein kinase (MAPK) cascade. Expression of HPK1 activates JNK1 specifically, and it elevates strongly AP-1-mediated transcriptional activity in vivo. HPK1 binds and phosphorylates MEKK1 directly, whereas JNK1 activation by HPK1 is inhibited by a dominant-negative MEKK1 or MKK4/SEK mutant. Interestingly, unlike PAK65, HPK1 does not contain the small GTPase Rac1/Cdc42-binding domain and does not bind to either Rac1 or Cdc42, suggesting that HPK1. activation is Rac1/Cdc42-independent. These results indicate that HPK1 is a novel functional activator of the JNK/SAPK signaling pathway.

Target	MAP4K1 (pS171)
Reactivity	Human
Host	Rabbit
Clonality	Polyclonal
Tested Applications	DB
Recommended dilutions	Optimal dilutions/concentrations should be determined by the end user.
Immunogen	KLH-conjugated synthetic phosphopeptide corresponding to amino acid residues surrounding S171 of human MAP4K1.
Purification	Purified in a 2-step procedure with the control and phosphorylated peptides. The phospho-specific antibody was eluted with high and low pH buffers and neutralized immediately, followed by dialysis against PBS.
Isotype	IgG
Conjugation	Unconjugated
Storage	Aliquot and store at -20°C. Avoid repeated freeze/thaw cycles.
Swiss Prot	Q92918
Buffer	PBS containing 0.09% sodium azide.
UNSPSC Code	12352203
Availability	Shipped within 5-10 working days.
Note	This product is for research use only.