Expression and potential functions of KIF3A/3B to promote nuclear reshaping and tail formation during Larimichthys polyactis spermiogenesis

Kinesin family member 3A induces related diseases via wingless-related integration site/β-catenin signaling pathway

Kinesin family member 3A is an important motor protein that participates in various physiological and pathological processes, including normal tissue development, homeostasis maintenance, tumor infiltration, and migration. The wingless-related integration site/β-catenin signaling pathway is essential for critical molecular mechanisms such as embryonic development, organogenesis, tissue regeneration, and carcinogenesis. Recent studies have examined the molecular mechanisms of kinesin family member 3A, among which the wingless-related integration site/β-catenin signaling pathway has gained attention. The interaction between kinesin family member 3A and the wingless-related integration site/β-catenin signaling pathway is compact and complex but is fascinating and worthy of further study. The upregulation and downregulation of kinesin family member 3A influence many diseases and patient survival through the wingless-related integration site/β-catenin signaling pathway. Therefore, this review mainly focuses on describing the kinesin family member 3A and wingless-related integration site/β-catenin signaling pathways and their associated diseases.

The potential function of KIF17 in large yellow croaker (Larimichthys crocea) spermatid remodeling: molecular characterization and expression pattern during spermiogenesis

KIF17, which belongs to the kinesin-2 protein family, plays an indispensable role in mammalian spermiogenesis. However, the role of KIF17 in fish spermatid remodeling during spermiogenesis remains poorly understood. Therefore, we aimed to study the role of KIF17 in spermatid remodeling during Larimichthys crocea (L. crocea) spermiogenesis. The kif17 cDNA sequence, 3247 bp in length, was cloned from L. crocea testis, which consisted of a 347-bp 5'-untranslated region (UTR), 413-bp 3' -UTR, and 2487-bp open reading frame. Bioinformatic analyses revealed that KIF17 obtained from L. crocea (Lc-KIF17) exhibited a high sequence identity compared with those from other teleosts and possessed the structural features of other kinesin-2 proteins. Based on structural similarity, we speculate that the role of Lc-KIF17 may be similar to that of KIF17 in other animals. Lc-kif17 mRNA was diffusely expressed in L. crocea tissues and was highly expressed in the testis, especially at stage IV testicular development. Immunofluorescence analysis revealed that Lc-KIF17 signals colocalized with β-tubulin signals and migrated from the perinuclear cytoplasm to the side of the nucleus where the tail forms during spermiogenesis. These findings revealed that KIF17 may be involved in L. crocea spermiogenesis. In particular, KIF17 may participate in spermatid remodeling by interacting with perinuclear microtubules during L. crocea spermiogenesis. Collectively, this study contributes to an improved understanding of the mechanism underlying L. crocea spermiogenesis and provides a basis for further research on L. crocea reproduction and development.

KIF3B gene silent variant leading to sperm morphology and motility defects and male infertility

Sperm structural and functional defects are leading causes of male infertility. Patients with immotile sperm disorders suffer from axoneme failure and show a significant reduction in sperm count. The kinesin family member 3B (KIF3B) is one of the genes involved in the proper formation of sperm with a critical role in intraflagellar and intramanchette transport. A part of exon 2 and exons 3–5 of the KIF3B encodes a protein coiled-coil domain that interacts with IFT20 from the IFT protein complex. In the present study, the coding region of KIF3B coiled-coil domain was assessed in 88 oligoasthenoteratozoospermic patients, and the protein expression was evaluated in the mature spermatozoa of the case and control groups using immunocytochemistry and western blotting. According to the results, there was no genetic variation in the exons 3–5 of the KIF3B, but a new A > T variant was identified within the exon 2 in 30 patients, where nothing was detected in the control group. In contrast to healthy individuals, significantly reduced protein expression was observable in oligoasthenoteratozoospermic (OAT) patients carrying variation where protein organization was disarranged, especially in the principal piece and midpiece of the sperm tail. Besides, the protein expression level was lower in the patients’ samples compared to that of the control group. According to the results of the present study the NM_004798.3:c.1032A > T, p.Pro344 = variant; which has been recently submitted to the Clinvar database; although synonymous, causes alterations in the transcription factor binding site, exon skipping, and also exonic splicing enhancer-binding site. Therefore, KIF3B can play an important role in spermatogenesis and the related protein reduction can cause male infertility.

Heterotrimeric Kinesin II is required for flagellar assembly and elongation of nuclear morphology during spermiogenesis in Schmidtea mediterranea

Development of sperm requires microtubule-based movements that drive assembly of a compact head and flagellated tails. Much is known about how flagella are built given their shared molecular core with motile cilia, but less is known about the mechanisms that shape the sperm head. The Kinesin Superfamily Protein 3A (KIF3A) pairs off with a second motor protein (KIF3B) and the Kinesin Associated Protein 3 (KAP3) to form Heterotrimeric Kinesin II. This complex drives intraflagellar transport (IFT) along microtubules during ciliary assembly. We show that KIF3A and KAP3 orthologs in Schmidtea mediterranea are required for axonemal assembly and nuclear elongation during spermiogenesis. Expression of Smed-KAP3 is enriched during planarian spermatogenesis with transcript abundance peaking in spermatocyte and spermatid cells. Disruption of Smed-kif3A or Smed-KAP3 expression by RNA-interference results in loss of spermatozoa and accumulation of unelongated spermatids. Confocal microscopy of planarian testis lobes stained with alpha-tubulin antibodies revealed that spermatids with disrupted Kinesin II function fail to assemble flagella, and visualization with 4',6-diamidino-2-phenylindole (DAPI) revealed reduced nuclear elongation. Disruption of Smed-kif3A or Smed-KAP3 expression also resulted in edema, reduced locomotion, and loss of epidermal cilia, which corroborates with somatic phenotypes previously reported for Smed-kif3B. These findings demonstrate that heterotrimeric Kinesin II drives assembly of cilia and flagella, as well as rearrangements of nuclear morphology in developing sperm. Prolonged activity of heterotrimeric Kinesin II in manchette-like structures with extended presence during spermiogenesis is hypothesized to result in the exaggerated nuclear elongation observed in sperm of turbellarians and other lophotrochozoans.

Motor proteins at the mitochondria-cytoskeleton interface

Mitochondria are multifunctional organelles that not only produce energy for the cell, but are also important for cell signalling, apoptosis and many biosynthetic pathways. In most cell types, they form highly dynamic networks that are constantly remodelled through fission and fusion events, repositioned by motor-dependent transport and degraded when they become dysfunctional. Motor proteins and their tracks are key regulators of mitochondrial homeostasis, and in this Review, we discuss the diverse functions of the three classes of motor proteins associated with mitochondria - the actin-based myosins, as well as the microtubule-based kinesins and dynein. In addition, Miro and TRAK proteins act as adaptors that link kinesin-1 and dynein, as well as myosin of class XIX (MYO19), to mitochondria and coordinate microtubule- and actin-based motor activities. Here, we highlight the roles of motor proteins and motor-linked track dynamics in the transporting and docking of mitochondria, and emphasize their adaptations in specialized cells. Finally, we discuss how motor-cargo complexes mediate changes in mitochondrial morphology through fission and fusion, and how they modulate the turnover of damaged organelles via quality control pathways, such as mitophagy. Understanding the importance of motor proteins for mitochondrial homeostasis will help to elucidate the molecular basis of a number of human diseases.

KIFC1 functions in nuclear reshaping and midpiece formation during the spermatogenesis of small yellow croaker Larimichthys polyactis

The C-terminal kinesin motor protein (KIFC1) has essential functions in spermatogenesis. To evaluate molecular mechanisms of KIFC1 during teleost fish spermatogenesis, there was cloning and sequencing the kifc1 cDNA in the testis of Larimichthys polyactis. Quantitative PCR results indicated there were Lp-kifc1 mRNA transcripts in the testes. Results from conducting fluorescence in situ hybridization and immunofluorescence procedures indicated there were trends in relative abundance changes in Lp-kifc1 mRNA transcripts that were associated with abundance of Lp-KIFC1 protein during spermatogenesis. The Lp-KIFC1 protein was detected at all stages of spermatogenesis. There was minimal Lp-KIFC1 in the cytoplasm of spermatogonia, with content being greater and concentrated in the perinuclear region in spermatocytes and during early/mid-stages of development of spermatids. There were large abundances of Lp-KIFC1 in spermatids at the mid-developmental stage. In late-developing spermatids, Lp-KIFC1 content was less and concentrated in the bottom of the nucleus, where the midpiece formed. There was a small Lp-KIFC1 in the midpiece of mature sperm. These findings indicate Lp-KIFC1 may have functions in L. polyactis spermatogenesis. Results from conducting immunofluorescence procedures indicated Lp-KIFC1 was co-localized microtubules and mitochondria throughout spermatogenesis. There were large abundances of Lp-KIFC1 and tubulin in spermatids during the mid-developmental stage, when there is a decrease in size and reshaping of the nucleus. During midpiece formation, there was co-localization of the Lp-KIFC1 and mitochondria in the spermatid perinuclear region to the midpiece. These findings indicate Lp-KIFC1 is involved in nuclear reshaping and midpiece formation during spermatogenesis in L. polyactis.

KIF3A regulates the Wnt/β-catenin pathway via transporting β-catenin during spermatogenesis in Eriocheir sinensis

The Wnt/β-catenin pathway participates in many important physiological events such as cell proliferation and differentiation in the male reproductive system. We found that Kinesin-2 motor KIF3A is highly expressed during spermatogenesis in Eriocheir sinensis; it may potentially promote the intracellular transport of cargoes in this process. However, only a few studies have focused on the relationship between KIF3A and the Wnt/β-catenin pathway in the male reproductive system of decapod crustaceans. In this study, we cloned and characterized the CDS of β-catenin in E. sinensis for the first time. Fluorescence in situ hybridization and immunofluorescence results showed the colocalization of Es-KIF3A and Es-β-catenin at the mRNA and the protein level respectively. To further explore the regulatory function of Es-KIF3A to the Wnt/β-catenin pathway, the es-kif3a was knocked down by double-stranded RNA (dsRNA) in vivo and in primary cultured cells in testes of E. sinensis. Results showed that the expression of es-β-catenin and es-dvl were decreased in the es-kif3a knockdown group. The protein expression level of Es-β-catenin was also reduced and the location of Es-β-catenin was changed from nucleus to cytoplasm in the late stage of spermatogenesis when es-kif3a was knocked down. Besides, the co-IP result demonstrated that Es-KIF3A could bind with Es-β-catenin. In summary, this study indicates that Es-KIF3A can positively regulate the Wnt/β-catenin pathway during spermatogenesis and Es-KIF3A can bind with Es-β-catenin to facilitate the nuclear translocation of Es-β-catenin.