|Coordinate||122,424,977 bp (GRCm38)|
|Base Change||A ⇒ T (forward strand)|
|Gene Name||protein kinase C, beta|
|Synonym(s)||Pkcb, Prkcb2, Prkcb1, A130082F03Rik, PKC-Beta|
|Chromosomal Location||122,288,751-122,634,402 bp (+)|
|MGI Phenotype||Mice homozygous and/or heterozygous for ENU-induced mutations exhibit abnormal B cell morphology and physiology, decreased IgM levels and reduced antibody response to a model T cell-independent antigen.|
|Amino Acid Change||Histidine changed to Leucine|
|Institutional Source||Beutler Lab|
|Gene Model||predicted gene model for protein(s): [ENSMUSP00000070019]|
AA Change: H75L
|Predicted Effect||probably damaging
PolyPhen 2 Score 1.000 (Sensitivity: 1.80; Specificity: 1.00)
|Phenotypic Category||T-independent B cell response defect- decreased TNP-specific IgM to TNP-Ficoll immunization|
|Alleles Listed at MGI|
|Mode of Inheritance||Autosomal Semidominant|
|Local Stock||Live Mice|
|Last Updated||05/13/2016 3:09 PM by Peter Jurek|
|Record Created||08/20/2013 6:38 PM by Kuan-Wen Wang|
The Tigris phenotype was identified among N-Nitroso-N-ethylurea (ENU)-mutagenized G3 mice of the pedigree R0409, some of which showed a diminished T-independent antibody response to 4-hydroxy-3-nitrophenylacetyl-Ficoll (NP-Ficoll) (Figure 1).
|Nature of Mutation|
Whole exome HiSeq sequencing of the G1 grandsire identified 54 mutations. The diminished T-independent antibody response to NP-Ficoll was linked by continuous variable mapping to a mutation in Prkcb: an A to T transversion at base pair 122,424,977 (v38) on chromosome 7, or base pair 135,898 in the GenBank genomic region NC_000073. Linkage was found with an additive model of linkage (P = 8.08 x 10-4), wherein two variant homozygotes and nine heterozygotes departed phenotypically from five homozygous reference mice (Figure 2). The mutation corresponds to residue 444 in the mRNA sequence NM_008855 within exon 3 of 17 total exons.
The mutated nucleotide is indicated in red. The mutation results in a histidine (H) to leucine (L) substitution at position 75 (H75L) in the PKCβ protein, and is strongly predicted by Polyphen-2 to cause loss of function (score = 0.966).
PKCβ is a member of the protein kinase C (PKC) family of serine-threonine kinases. The PKC family belongs to the AGC-type kinase (protein kinase A/protein kinase G/protein kinase C) superfamily. PKC kinases share certain structural features including a highly conserved catalytic domain consisting of motifs required for ATP-substrate binding and catalysis, and a regulatory domain that maintains the enzyme in an inactive conformation. The regulatory and catalytic domains are attached to each other by a hinge region (Figure 3). Conventional PKCs (cPKCs) contain five variable (V) domains and four conserved (C) domains. In PKCβ isoforms, the C1 domain occurs at residues 36-151 and can be subdivided into an A and B domain, each containing a characteristic DAG-binding motif, HX12CX2CXnCX2CX4HX2CX7C, where H is histidine, C is cysteine, X is any other amino acid, and n is 13 or 14 (1).
The Tigris mutation results in the substitution of a histidine for a leucine at amino acid 75 within the C1A domain.
Please see the record Untied for information about Prkcb.
In B cell receptor signaling, PKCβ functions to upregulate NF-κB activity and to promote B-cell activation, PKCβ can also directly inhibit Btk through a negative feedback loop (2). PKCβ specifically phosphorylates Btk at Ser180 within its Tec-homology (TH) region, leading to an inhibition of Btk membrane translocation and activation, and the downstream events that promote PKCβ activation. PKCβ activity also appears to play a role in mediating B cell activating factor (BAFF)-induced signals leading to B cell survival by phosphorylating the Akt kinase (also known as protein kinase B or PKB) and contributing to its activation.
A targeted knockout of the Prkcb gene in mice resulted in animals with reduced numbers of mature peripheral B cells, a loss of peritoneal B-1 B cells, reduced T cell-independent antibody responses, as well as reduced function of various other immune cell types. The reduction of B cell antibody responses to TNP-Ficoll in Tigris mice suggests that the function of B-1 and/or MZ B cells is impaired in these animals with BCR signaling likely affected. These phenotypes are consistent with the phenotypes observed in Prkcb-/-animals, which also exhibit reduced T cell-independent antibody responses along with severe impairment of B-1 cells (3). The semidominant phenotype observed in Tigris mice may be due to the expression of nonfunctional, but appropriately localized, PKCβ proteins that are then able to inhibit the appropriate localization and function of wild type kinases.
Tigris(F):5'- ATGTGTGCAGTGGAGCCAGGTA -3'
Tigris(R):5'- GCACGATCAGAGTGAGGTCCTAGT -3'
Tigris_seq(F):5'- tcctgtctctgcctcctg -3'
Tigris_seq(R):5'- CAGAGTGAGGTCCTAGTTGTTTCC -3'
1. Steinberg, S. F. (2008) Structural Basis of Protein Kinase C Isoform Function. Physiol Rev. 88, 1341-1378.
2. Kang, S. W., Wahl, M. I., Chu, J., Kitaura, J., Kawakami, Y., Kato, R. M., Tabuchi, R., Tarakhovsky, A., Kawakami, T., Turck, C. W., Witte, O. N., and Rawlings, D. J. (2001) PKCbeta Modulates Antigen Receptor Signaling Via Regulation of Btk Membrane Localization. EMBO J. 20, 5692-5702.
|Science Writers||Anne Murray|
|Authors||Kuan-Wen Wang, Jin Huk Choi, Ming Zeng, Bruce Beutler|