Anti-LKB1/STK11 Antibody Picoband® Fluoro488 Conjugated

Serine/threonine kinase 11 or LKB1 is a protein kinase which in humans is encoded by the STK11 gene. The STK11 gene, which encodes a member of the serine/threonine kinase, regulates cell polarity and functions as a tumour suppressor. STK11 is a primary upstream kinase of adenine monophosphate-activated protein kinase (AMPK), a necessary element in cell metabolism that is required for maintaining energy homeostasis. It has been found that LKB1 physically associates with p53 and regulates specific p53-dependent apoptosis pathways. The STK11 gene extends over 23 kb of genomic DNA and is composed of 9 exons, which are transcribed in telomere-to-centromere ion.

E.coli-derived human LKB1 recombinant protein (Position: K62-C430) . Human LKB1 shares 89% amino acid (aa) sequence identity with both mouse and rat LKB1.

Tumor suppressor serine/threonine-protein kinase that controls the activity of AMP-activated protein kinase (AMPK) family members, thereby playing a role in various processes such as cell metabolism, cell polarity, apoptosis and DNA damage response. Acts by phosphorylating the T-loop of AMPK family proteins, thus promoting their activity: phosphorylates PRKAA1, PRKAA2, BRSK1, BRSK2, MARK1, MARK2, MARK3, MARK4, NUAK1, NUAK2, SIK1, SIK2, SIK3 and SNRK but not MELK. Also phosphorylates non- AMPK family proteins such as STRADA, PTEN and possibly p53/TP53. Acts as a key upstream regulator of AMPK by mediating phosphorylation and activation of AMPK catalytic subunits PRKAA1 and PRKAA2 and thereby regulates processes including: inhibition of signaling pathways that promote cell growth and proliferation when energy levels are low, glucose homeostasis in liver, activation of autophagy when cells undergo nutrient deprivation, and B-cell differentiation in the germinal center in response to DNA damage. Also acts as a regulator of cellular polarity by remodeling the actin cytoskeleton. Required for cortical neuron polarization by mediating phosphorylation and activation of BRSK1 and BRSK2, leading to axon initiation and specification. Involved in DNA damage response: interacts with p53/TP53 and recruited to the CDKN1A/WAF1 promoter to participate in transcription activation. Able to phosphorylate p53/TP53; the relevance of such result in vivo is however unclear and phosphorylation may be in and mediated by downstream STK11/LKB1 kinase NUAK1. Also acts as a mediator of p53/TP53-dependent apoptosis via interaction with p53/TP53: translocates to the mitochondrion during apoptosis and regulates p53/TP53-dependent apoptosis pathways. In vein endothelial cells, inhibits PI3K/Akt signaling activity and thus induces apoptosis in response to the oxidant peroxynitrite (in vitro) . Regulates UV radiation-induced DNA damage response mediated by CDKN1A. In association with NUAK1, phosphorylates CDKN1A in response to UV radiation and contributes to its degradation which is necessary for optimal DNA repair (PubMed:25329316) . .

1. Brown KA, McInnes KJ, Takagi K, Ono K, Hunger NI, Wang L, Sasano H, Simpson ER (November 2011) . LKB1 expression is inhibited by estradiol-17β in MCF-7 cells. J. Steroid Biochem. Mol. Biol. 127 (3-5) : 439–43. 2. Jenne DE, Reimann H, Nezu J, Friedel W, Loff S, Jeschke R, Müller O, Back W, Zimmer M (January 1998) . Peutz-Jeghers syndrome is caused by mutations in a novel serine threonine kinase.

Nucleus. Cytoplasm. Membrane . Mitochondrion. A small fraction localizes at membranes (By similarity) . Relocates to the cytoplasm when bound to STRAD (STRADA or STRADB) and CAB39/MO25 (CAB39/MO25alpha or CAB39L/MO25beta) . Translocates to the mitochondrion during apoptosis. Translocates to the cytoplasm in response to metformin or peroxynitrite treatment. PTEN promotes cytoplasmic localization. .