Caspase recruitment domain protein 6 is a microtubule-interacting protein that positively modulates NF-κB activation

Abstract

Proteins containing a caspase recruitment domain (CARD) play pivotal roles in signal transduction leading to apoptosis and NF-B activation and inflammation. Here we identify and characterize human and mouse CARD protein 6 (CARD6), CARD-containing proteins of unique structure. CARD6 associates with microtubules and interacts with receptor-interacting protein (RIP)-like interacting caspase-like apoptosis regulatory protein kinase (RICK), a CARD-containing member of the RIP family of protein kinases. These kinases are involved in multiple NF-B signaling pathways important for innate and adaptive immune responses. Surprisingly, the CARDs of CARD6 and RICK were not required for their interaction; instead, mutational analysis revealed that the CARD of CARD6 negatively controls the association of these molecules. CARD6 also binds to RIP1, a RIP kinase homologue that lacks a CARD but contains a C-terminal death domain. Coexpression of RICK targets CARD6 to aggresomes via a mechanism that requires the CARD of RICK. Importantly, CARD6 expression has a synergistic effect on NF-B activation induced by several independent signal transduction pathways. In summary, our results indicate that CARD6 is a regulator of NF-B activation that modulates the functions of RIP kinase family members.signal transduction ͉ immunity ͉ receptor-interacting protein kinases

Rapid emergence and mechanisms of resistance by U87 glioblastoma cells to doxorubicin in an in vitro tumor microfluidic ecology

“…From the exome sequencing data, we further identified three mutated genes (CARD6, NSD1, and NLRP13) that are associated with NF-κB activation. CARD6 (caspase activation and recruitment domain family, member 6) negatively regulates NF-κB activation by NOD1 (nucleotide-binding oligomerization domain containing 1) receptor in human embryonic kidney-derived HEK293T cells (20,21) whereas the effect is reversed in Huh7 cells of hepatocarcinoma origin (22), thus indicating that the role of CARD6 in NF-κB activation may be cell-type specific.…”

CARD6 Is Interferon Inducible but Not Involved in Nucleotide-Binding Oligomerization Domain Protein Signaling Leading to NF-κB Activation

“…Although much progress has been made in assigning precise roles to most CARD-containing proteins, the functions of the 1,037-amino-acid (aa) human and 1,175-aa mouse CARD6 proteins are still unknown. CARD6 has a unique structure in that it contains the CARD at the N terminus, a glutamic acid-rich region following the CARD, and a proline-rich region at the C terminus (7). CARD6 also harbors a ϳ350-aa region with similarity to upregulated gene 4 (URG4), a protein that is induced in response to hepatitis Bx antigen overexpression and exerts a positive effect on proliferation (36).…”

“…Our initial characterization of human CARD6 showed that this protein associates with microtubules in a CARD-and proline-rich region-dependent manner (7). CARD6 also interacts with RIP2 (also known as RICK or CARDIAK), a CARD-containing member of the RIP family of protein kinases (25).…”

“…Conversely, the CARD of RIP2 mediates the translocation of CARD6 to aggresomes (7). Moreover, human CARD6 enhances NK-B activation mediated by several independent pathways.…”

“…Proteins were visualized using secondary horseradish peroxidase-coupled anti-rabbit antibody (Amersham) followed by ECL (Amersham). The polyclonal antibody raised against endogenous mouse CARD6 has been described previously (7). Endogenous RIP2 was detected with polyclonal anti-RIP2 antibody (no.…”