Multifunctional protein 4.1R regulates the asymmetric segregation of Numb during terminal erythroid maturation

Cytoskeletal Protein 4.1R in Health and Diseases

The protein 4.1R is an essential component of the erythrocyte membrane skeleton, serving as a key structural element and contributing to the regulation of the membrane's physical properties, including mechanical stability and deformability, through its interaction with spectrin-actin. Recent research has uncovered additional roles of 4.1R beyond its function as a linker between the plasma membrane and the membrane skeleton. It has been found to play a crucial role in various biological processes, such as cell fate determination, cell cycle regulation, cell proliferation, and cell motility. Additionally, 4.1R has been implicated in cancer, with numerous studies demonstrating its potential as a diagnostic and prognostic biomarker for tumors. In this review, we provide an updated overview of the gene and protein structure of 4.1R, as well as its cellular functions in both physiological and pathological contexts.

Bag3 Regulates Mitochondrial Function and the Inflammasome Through Canonical and Noncanonical Pathways in the Heart

B-cell lymphoma 2-associated athanogene-3 (Bag3) is expressed in all animal species, with Bag3 levels being most prominent in the heart, the skeletal muscle, the central nervous system, and in many cancers. Preclinical studies of Bag3 biology have focused on animals that have developed compromised cardiac function; however, the present studies were performed to identify the pathways perturbed in the heart even before the occurrence of clinical signs of dilatation and failure of the heart. These studies show that hearts carrying variants that knockout one allele of BAG3 have significant alterations in multiple cellular pathways including apoptosis, autophagy, mitochondrial homeostasis, and the inflammasome.

PQBP1 regulates striatum development through balancing striatal progenitor proliferation and differentiation

The balance between cell proliferation and differentiation is essential for maintaining the neural progenitor pool and brain development. Although the mechanisms underlying cell proliferation and differentiation at the transcriptional level have been studied intensively, post-transcriptional regulation of cell proliferation and differentiation remains largely unclear. Here, we show that deletion of the alternative splicing regulator PQBP1 in striatal progenitors results in defective striatal development due to impaired neurogenesis of spiny projection neurons (SPNs). Pqbp1-deficient striatal progenitors exhibit declined proliferation and increased differentiation, resulting in a reduced striatal progenitor pool. We further reveal that PQBP1 associates with components in splicing machinery. The alternative splicing profiles identify that PQBP1 promotes the exon 9 inclusion of Numb, a variant that mediates progenitor proliferation. These findings identify PQBP1 as a regulator in balancing striatal progenitor proliferation and differentiation and provide alternative insights into the pathogenic mechanisms underlying Renpenning syndrome.

BAG3: Nature's Quintessential Multi-Functional Protein Functions as a Ubiquitous Intra-Cellular Glue

BAG3 is a 575 amino acid protein that is found throughout the animal kingdom and homologs have been identified in plants. The protein is expressed ubiquitously but is most prominent in cardiac muscle, skeletal muscle, the brain and in many cancers. We describe BAG3 as a quintessential multi-functional protein. It supports autophagy of both misfolded proteins and damaged organelles, inhibits apoptosis, maintains the homeostasis of the mitochondria, and facilitates excitation contraction coupling through the L-type calcium channel and the beta-adrenergic receptor. High levels of BAG3 are associated with insensitivity to chemotherapy in malignant cells whereas both loss of function and gain of function variants are associated with cardiomyopathy.

The protein 4.1R downregulates VEGFA in M2 macrophages to inhibit colon cancer metastasis

M2 macrophages are crucial components of the tumour microenvironment and have been shown to be closely related to tumour progression. Co-culture with 4.1R^-/- M2 macrophages enhances the malignancy of colon cancer (CC), but the mechanism remains unclear. Here, we report that protein 4.1R knockout reduced the phagocytosis of M2 macrophages (M-CSF/IL-4-treated bone marrow cells) and promoted MC38 colon cancer cell proliferation, migration, invasion, tumour formation and epithelial-mesenchymal transition (EMT), which are regulated by M2 macrophages. Further mechanistic dissection revealed that the 4.1R knockout upregulated vascular endothelial growth factor A (VEGFA) secreted by M2 macrophages and promoted colon cancer progression by activating the PI3K/AKT signalling pathway. In summary, our present study identified that 4.1R downregulates VEGFA secretion in M2 macrophages and delays the malignant potential of colon cancer by inhibiting the PI3K/AKT signalling pathway.