Microtubule associated protein 4 phosphorylation leads to pathological cardiac remodeling in mice

Abstract

BackgroundCardiac remodeling is a pathophysiological process that involves various changes in heart, including cardiac hypertrophy and fibrosis. Cardiac remodeling following pathological stimuli is common trigger leading to cardiac maladaptation and onset of heart failure, and their pathogenesis remains unclear.MethodsHeart specimens of tetralogy of Fallot (TOF) patients, myocardial infarction (MI) and transverse aortic constriction (TAC) mouse models were collected to determine changes of microtubule associated protein 4 (MAP4) phosphorylation. MAP4 (S667A, S737E and S760E) knock in (MAP4 KI) mouse and cultured neonatal mouse cardiomyocytes or fibroblasts were used to investigate changes of cardiac phenotypes and possible mechanisms with a variety of approaches, including functional, histocytological and pathological observations.FindingsElevated cardiac phosphorylation of MAP4 (S737 and S760) was observed in TOF patients, MI and TAC mouse models. In MAP4 KI mice, age-dependent cardiac phenotypes, including cardiac hypertrophy, fibrosis, diastolic and systolic dysfunction were observed. In addition, increased cardiomyocyte apoptosis together with microtubule disassembly and mitochondrial translocation of phosphorylated MAP4 was detected prior to the onset of cardiac remodeling, and p38/MAPK was demonstrated to be the possible signaling pathway that mediated MAP4 (S737 and S760) phosphorylation.InterpretationOur data reveal for the first time that MAP4 drives pathological cardiac remodeling through its phosphorylation. These findings bear the therapeutic potential to ameliorate pathological cardiac remodeling by attenuating MAP4 phosphorylation.FundThis work was supported by the Key Program of National Natural Science Foundation of China (No.81430042) and National Natural Science Foundation of China (No.81671913).

Supporting the heart: Functions of the cardiomyocyte's non-sarcomeric cytoskeleton

“…Other groups have found that MAP4 itself becomes de-phosphorylated at serines 924 and 1056 during cardiac pathological hypertrophy, contributing to the densification of the microtubule network [124]. Contrastingly, another study reported increased phosphorylation of serines 737 and 760 during pressure overload surgery in mice [125]. Clearly the phosphorylation of MAP4 is a complicated picture, and more studies are needed to understand the relative contributions of these phosphorylation sites to MAP4 and microtubule biology.…”

MAP4 as a New Candidate in Cardiovascular Disease

“…Briefly, mice exhibiting MAP4 phosphorylation exerted age-dependent effects such as pathological cardiac remodeling, cardiomyocyte mitochondrial apoptosis and disruption, and systolic and diastolic dysfunction. As such, MT disassembly, translocation of phosphorylated MAP4, and cardiomyocyte apoptosis are deemed important factors in initiating cardiac remodeling, with the activation of p38/MAPK being suggested as the crucial upstream kinase involved in the MAP4 phosphorylation (Li et al, 2018) FIGURE 1 | Schematic illustrating the role of MAP4 in CVD. Inflammation, hypoxia, ischemia, etc., stimulate the activation of the MKK6/p38 MAPK pathway.…”

Microtubule-associated protein 4 phosphorylation regulates epidermal keratinocyte migration and proliferation

“…The KI mice were constructed and identified by the Shanghai Biomodel Organism Science & Technology Development Co., Ltd. Cas9 mRNA, guide RNAs and the donor vector were microinjected into fertilized eggs (C57BL/6J) before the eggs were implanted into surrogate C57BL/6J females as described in our previous study [19].…”

“…(1:1000, Bethyl, USA), p-MAP4(S768) (Biolegend, 1:1000), p-MAP4(S696) (1:1000, GL Biochem), p-MAP4(S787) (1:1000, GL Biochem), p-MAP4(S737) (1:1000, GL Biochem), β-Actin (1:1000, Cell Signaling Technology), PCNA (1:1000, Abcam), and Ki67 (1:1000, Abcam). The rabbit polyclonal antibodies against p-MAP4(S696), p-MAP4(S787) and p-MAP4(S737) were developed in house as described and validated in our previous report [19]. Here, we validated the in-house rabbit polyclonal antibody against p-MAP4 using the amino acids QAKVG(pS)LDNVGHLPAGc and the respective nonphosphorylated peptides conjugated to bovine serum albumin (BSA) ( Supplementary Fig.…”

“…To assess the potential effect of elevated MAP4 phosphorylation on epidermal wound healing in vivo, we constructed a mutant KI mouse model that mimicked MAP4 phosphorylation at specific sites (S737 and S760) ( Supplementary Fig. 2) [19]. Macroscopically, the wound closure area, quantified at different time points following wounding, showed that, from day 5 post wounding, healing was significantly accelerated in the KI group compared with the wild-type (WT) group (Fig.…”