PKN1 kinase-negative knock-in mice develop splenomegaly and leukopenia at advanced age without obvious autoimmune-like phenotypes

Abstract

Protein kinase N1 (PKN1) knockout (KO) mice spontaneously form germinal centers (GCs) and develop an autoimmune-like disease with age. Here, we investigated the function of PKN1 kinase activity in vivo using aged mice deficient in kinase activity resulting from the introduction of a point mutation (T778A) in the activation loop of the enzyme. PKN1[T778A] mice reached adulthood without external abnormalities; however, the average spleen size and weight of aged PKN1[T778A] mice increased significantly compared to aged wild type (WT) mice. Histologic examination and Southern blot analyses of spleens showed extramedullary hematopoiesis and/or lymphomagenesis in some cases, although without significantly different incidences between PKN1[T778A] and WT mice. Additionally, flow cytometry revealed increased numbers in B220+, CD3+, Gr1+ and CD193+ leukocytes in the spleen of aged PKN1[T778A] mice, whereas the number of lymphocytes, neutrophils, eosinophils, and monocytes was reduced in the peripheral blood, suggesting an advanced impairment of leukocyte trafficking with age. Moreover, aged PKN1[T778A] mice showed no obvious GC formation nor autoimmune-like phenotypes, such as glomerulonephritis or increased anti-dsDNA antibody titer, in peripheral blood. Our results showing phenotypic differences between aged Pkn1-KO and PKN1[T778A] mice may provide insight into the importance of PKN1-specific kinase-independent functions in vivo.

Genomic and phenotypic analysis of SspH1 identifies a new Salmonella effector, SspH3

“…expression is particularly high in lymphoid tissues where it is associated with leukocyte development and their migration (Mashud et al, 2017;Siddique et al, 2019). Our work confirms these previous observations showing that PKN1 is strongly expressed in the monocyte cell line U937 and is nominally expressed in the epithelial cells tested (Figure 1a).…”

“…PKN1 expression varies across mammalian in vitro cell lines and is largely tissue‐type specific (Cell atlas—PKN1—The Human Protein Atlas, n.d.; Lachmann et al., 2011; Thul et al., 2017). PKN1 expression is particularly high in lymphoid tissues where it is associated with leukocyte development and their migration (Mashud et al., 2017; Siddique et al., 2019). Our work confirms these previous observations showing that PKN1 is strongly expressed in the monocyte cell line U937 and is nominally expressed in the epithelial cells tested (Figure 1a).…”

“…Furthermore, Pkn1 knockouts in mice and cerebellar granule cells display an increase in basal p‐Akt S437 (zur Nedden et al., 2018; Yasui et al., 2012). However, knock‐in of kinase dead Pkn1 is not associated with an increase in basal p‐Akt S473 in mice (Siddique et al., 2019). Our work demonstrates that knockdown of PKN1 in U937 cells increases p‐Akt S473 levels at basal conditions, during serum starvation, and following serum re‐introduction (Figure 3a).…”

Genotype-driven therapeutic developments in Parkinson’s disease

“…In addition, optimized antibodies have been developed in preclinical models against different forms of mono-, oligomeric, fibrils, and aggregated forms to target different stages in α-synuclein related pathophysiology (Wang et al 2019 ). Moreover, the recent development of the SNCA gene by antisense-oligonucleotides (ASOs; short-chain, synthetic, single-stranded oligonucleotides that bind to the complementary mRNA and modify/hinder their respective translation) has already been proven useful in in-vitro, rodent, and primate models (Uehara et al 2019 ; Alarcón-Arís et al 2018 ; Choong and Mochizuki 2017 ).…”

The structure and function of protein kinase C-related kinases (PRKs)

“…PRK1 has been implicated in lymphocyte trafficking by studies with a PRK1 kinase-inactive knock-in mouse [ 99 ], whose lymphocytes displayed reduced migration from secondary lymphoid organs to the blood and lymph. The same mouse model indicated that PRK1 also regulates trafficking of all leukocytes [ 100 ].…”